diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_auto_translate.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_auto_translate.js
index edf906d5ded3..ceb72858cd62 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_auto_translate.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_auto_translate.js
@@ -38,19 +38,21 @@ add_task(async function test_translations_telemetry_auto_translate() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(
     Glean.translationsPanel.alwaysTranslateLanguage,
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "es"],
+      assertForMostRecentEvent: {
+        language: "es",
+      },
     }
   );
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.close, {
@@ -66,9 +68,9 @@ add_task(async function test_translations_telemetry_auto_translate() {
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [
-        value => value.extra.request_target === "full-page",
-      ],
+      assertForMostRecentEvent: {
+        request_target: "full-page",
+      },
     }
   );
 
@@ -81,12 +83,12 @@ add_task(async function test_translations_telemetry_auto_translate() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "revisitView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "revisitView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_basics.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_basics.js
index 30a1e19c7e82..06d394cf3738 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_basics.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_basics.js
@@ -31,12 +31,12 @@ add_task(async function test_translations_telemetry_basics() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
@@ -61,12 +61,12 @@ add_task(async function test_translations_telemetry_basics() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_open_panel.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_open_panel.js
index a49059f78fe9..f4744bdcd168 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_open_panel.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_open_panel.js
@@ -30,12 +30,12 @@ add_task(async function test_translations_telemetry_open_panel() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
@@ -60,12 +60,12 @@ add_task(async function test_translations_telemetry_open_panel() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer.js
index 93ff47385163..5b47a5dae91b 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer.js
@@ -18,12 +18,12 @@ add_task(async function test_translations_panel_auto_offer() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "true",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: true,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
@@ -58,12 +58,12 @@ add_task(async function test_translations_panel_auto_offer() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "true",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: true,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer_settings.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer_settings.js
index 4a2959f58ea7..785d75da448d 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer_settings.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_panel_auto_offer_settings.js
@@ -35,12 +35,12 @@ add_task(async function test_translations_panel_auto_offer_settings() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await FullPageTranslationsTestUtils.clickAlwaysOfferTranslations();
@@ -50,7 +50,9 @@ add_task(async function test_translations_panel_auto_offer_settings() {
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      allValuePredicates: [value => value.extra.toggled_on === "true"],
+      assertForAllEvents: {
+        toggled_on: true,
+      },
     }
   );
 
@@ -66,12 +68,12 @@ add_task(async function test_translations_panel_auto_offer_settings() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: true,
-    allValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForAllEvents: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await TestTranslationsTelemetry.assertEvent(
@@ -98,12 +100,12 @@ add_task(async function test_translations_panel_auto_offer_settings() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 3,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "true",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: true,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
 
   await cleanup();
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_switch_languages.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_switch_languages.js
index 41183cc9cffd..5ba51751f32d 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_switch_languages.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_switch_languages.js
@@ -29,19 +29,21 @@ add_task(async function test_translations_telemetry_switch_from_language() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(
     Glean.translationsPanel.changeFromLanguage,
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "en"],
+      assertForMostRecentEvent: {
+        language: "en",
+      },
     }
   );
 
@@ -52,7 +54,9 @@ add_task(async function test_translations_telemetry_switch_from_language() {
     {
       expectedEventCount: 2,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "es"],
+      assertForMostRecentEvent: {
+        language: "es",
+      },
     }
   );
 
@@ -72,7 +76,9 @@ add_task(async function test_translations_telemetry_switch_from_language() {
     {
       expectedEventCount: 3,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "en"],
+      assertForMostRecentEvent: {
+        language: "en",
+      },
     }
   );
 
@@ -105,19 +111,21 @@ add_task(async function test_translations_telemetry_switch_to_language() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(
     Glean.translationsPanel.changeToLanguage,
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "fr"],
+      assertForMostRecentEvent: {
+        language: "fr",
+      },
     }
   );
 
@@ -128,7 +136,9 @@ add_task(async function test_translations_telemetry_switch_to_language() {
     {
       expectedEventCount: 2,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "en"],
+      assertForMostRecentEvent: {
+        language: "en",
+      },
     }
   );
 
@@ -148,7 +158,9 @@ add_task(async function test_translations_telemetry_switch_to_language() {
     {
       expectedEventCount: 3,
       expectNewFlowId: false,
-      finalValuePredicates: [value => value.extra.language === "en"],
+      assertForMostRecentEvent: {
+        language: "en",
+      },
     }
   );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_failure.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_failure.js
index 7a1c1e4813d6..5558a4de8c49 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_failure.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_failure.js
@@ -51,12 +51,12 @@ add_task(
     await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
       expectedEventCount: 1,
       expectNewFlowId: true,
-      finalValuePredicates: [
-        value => value.extra.auto_show === "false",
-        value => value.extra.view_name === "defaultView",
-        value => value.extra.opened_from === "translationsButton",
-        value => value.extra.document_language === "es",
-      ],
+      assertForMostRecentEvent: {
+        auto_show: false,
+        view_name: "defaultView",
+        opened_from: "translationsButton",
+        document_language: "es",
+      },
     });
 
     await FullPageTranslationsTestUtils.clickTranslateButton({
@@ -69,12 +69,12 @@ add_task(
     await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
       expectedEventCount: 2,
       expectNewFlowId: false,
-      finalValuePredicates: [
-        value => value.extra.auto_show === "true",
-        value => value.extra.view_name === "errorView",
-        value => value.extra.opened_from === "translationsButton",
-        value => value.extra.document_language === "es",
-      ],
+      assertForMostRecentEvent: {
+        auto_show: true,
+        view_name: "errorView",
+        opened_from: "translationsButton",
+        document_language: "es",
+      },
     });
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsPanel.translateButton,
@@ -103,24 +103,23 @@ add_task(
     await TestTranslationsTelemetry.assertEvent(Glean.translations.error, {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [
-        value =>
-          value.extra.reason === "Error: Intentionally rejecting downloads.",
-      ],
+      assertForMostRecentEvent: {
+        reason: "Error: Intentionally rejecting downloads.",
+      },
     });
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
         expectNewFlowId: false,
-        finalValuePredicates: [
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.document_language === "es",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "full-page",
-        ],
+        assertForMostRecentEvent: {
+          from_language: "es",
+          to_language: "en",
+          auto_translate: false,
+          document_language: "es",
+          top_preferred_language: "en",
+          request_target: "full-page",
+        },
       }
     );
 
@@ -162,12 +161,12 @@ add_task(async function test_translations_telemetry_auto_translation_failure() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "true",
-      value => value.extra.view_name === "errorView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: true,
+      view_name: "errorView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.close, {
     expectedEventCount: 0,
@@ -176,24 +175,23 @@ add_task(async function test_translations_telemetry_auto_translation_failure() {
   await TestTranslationsTelemetry.assertEvent(Glean.translations.error, {
     expectedEventCount: 1,
     expectNewFlowId: false,
-    finalValuePredicates: [
-      value =>
-        value.extra.reason === "Error: Intentionally rejecting downloads.",
-    ],
+    assertForMostRecentEvent: {
+      reason: "Error: Intentionally rejecting downloads.",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(
     Glean.translations.translationRequest,
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [
-        value => value.extra.from_language === "es",
-        value => value.extra.to_language === "en",
-        value => value.extra.auto_translate === "true",
-        value => value.extra.document_language === "es",
-        value => value.extra.top_preferred_language === "en",
-        value => value.extra.request_target === "full-page",
-      ],
+      assertForMostRecentEvent: {
+        from_language: "es",
+        to_language: "en",
+        auto_translate: true,
+        document_language: "es",
+        top_preferred_language: "en",
+        request_target: "full-page",
+      },
     }
   );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_request.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_request.js
index 3ebcd0dd411b..b5ed98d9bd0e 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_request.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_translation_request.js
@@ -69,12 +69,12 @@ add_task(async function test_translations_telemetry_manual_translation() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "translationsButton",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "translationsButton",
+      document_language: "es",
+    },
   });
   await TestTranslationsTelemetry.assertEvent(
     Glean.translationsPanel.translateButton,
@@ -92,14 +92,14 @@ add_task(async function test_translations_telemetry_manual_translation() {
     {
       expectedEventCount: 1,
       expectNewFlowId: false,
-      finalValuePredicates: [
-        value => value.extra.from_language === "es",
-        value => value.extra.to_language === "en",
-        value => value.extra.auto_translate === "false",
-        value => value.extra.document_language === "es",
-        value => value.extra.top_preferred_language === "en",
-        value => value.extra.request_target === "full-page",
-      ],
+      assertForMostRecentEvent: {
+        from_language: "es",
+        to_language: "en",
+        auto_translate: false,
+        document_language: "es",
+        top_preferred_language: "en",
+        request_target: "full-page",
+      },
     }
   );
 
@@ -157,14 +157,14 @@ add_task(async function test_translations_telemetry_auto_translation() {
     {
       expectedEventCount: 1,
       expectNewFlowId: true,
-      finalValuePredicates: [
-        value => value.extra.from_language === "es",
-        value => value.extra.to_language === "en",
-        value => value.extra.auto_translate === "true",
-        value => value.extra.document_language === "es",
-        value => value.extra.top_preferred_language === "en",
-        value => value.extra.request_target === "full-page",
-      ],
+      assertForMostRecentEvent: {
+        from_language: "es",
+        to_language: "en",
+        auto_translate: true,
+        document_language: "es",
+        top_preferred_language: "en",
+        request_target: "full-page",
+      },
     }
   );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_unsupported_lang.js b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_unsupported_lang.js
index 838e30cb1af8..2599baae1c8f 100644
--- a/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_unsupported_lang.js
+++ b/browser/components/translations/tests/browser/browser_translations_full_page_telemetry_unsupported_lang.js
@@ -26,12 +26,12 @@ add_task(async function test_translations_telemetry_unsupported_lang() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 1,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "appMenu",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "appMenu",
+      document_language: "es",
+    },
   });
 
   await FullPageTranslationsTestUtils.clickChangeSourceLanguageButton({
@@ -52,12 +52,12 @@ add_task(async function test_translations_telemetry_unsupported_lang() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 2,
     expectNewFlowId: false,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "appMenu",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "appMenu",
+      document_language: "es",
+    },
   });
 
   await FullPageTranslationsTestUtils.clickCancelButton();
@@ -84,12 +84,12 @@ add_task(async function test_translations_telemetry_unsupported_lang() {
   await TestTranslationsTelemetry.assertEvent(Glean.translationsPanel.open, {
     expectedEventCount: 3,
     expectNewFlowId: true,
-    finalValuePredicates: [
-      value => value.extra.auto_show === "false",
-      value => value.extra.view_name === "defaultView",
-      value => value.extra.opened_from === "appMenu",
-      value => value.extra.document_language === "es",
-    ],
+    assertForMostRecentEvent: {
+      auto_show: false,
+      view_name: "defaultView",
+      opened_from: "appMenu",
+      document_language: "es",
+    },
   });
 
   await FullPageTranslationsTestUtils.clickDismissErrorButton();
diff --git a/browser/components/translations/tests/browser/browser_translations_select_telemetry_init_failure_ui.js b/browser/components/translations/tests/browser/browser_translations_select_telemetry_init_failure_ui.js
index 14d97c82defa..18a07c625d54 100644
--- a/browser/components/translations/tests/browser/browser_translations_select_telemetry_init_failure_ui.js
+++ b/browser/components/translations/tests/browser/browser_translations_select_telemetry_init_failure_ui.js
@@ -26,12 +26,12 @@ add_task(
       {
         expectedEventCount: 1,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
@@ -64,12 +64,12 @@ add_task(
       {
         expectedEventCount: 2,
         expectNewFlowId: false,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
@@ -104,12 +104,12 @@ add_task(
       {
         expectedEventCount: 3,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
@@ -140,32 +140,31 @@ add_task(
       {
         expectedEventCount: 4,
         expectNewFlowId: false,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "2064" // With carriage returns
-              : "2041"), // No carriage returns
-          value => value.extra.source_text_word_count === "358",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 2064 // With carriage returns
+              : 2041, // No carriage returns
+          source_text_word_count: 358,
+        },
       }
     );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_select_telemetry_primary_ui.js b/browser/components/translations/tests/browser/browser_translations_select_telemetry_primary_ui.js
index 9d913acff638..47b8bd57a28a 100644
--- a/browser/components/translations/tests/browser/browser_translations_select_telemetry_primary_ui.js
+++ b/browser/components/translations/tests/browser/browser_translations_select_telemetry_primary_ui.js
@@ -41,28 +41,28 @@ add_task(
       {
         expectedEventCount: 1,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.source_text_code_units === "165",
-          value => value.extra.source_text_word_count === "28",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units: 165,
+          source_text_word_count: 28,
+        },
       }
     );
 
@@ -83,16 +83,16 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 2,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fi",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.source_text_code_units === "165",
-          value => value.extra.source_text_word_count === "28",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fi",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units: 165,
+          source_text_word_count: 28,
+        },
       }
     );
 
@@ -131,28 +131,28 @@ add_task(
       {
         expectedEventCount: 2,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 3,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.source_text_code_units === "165",
-          value => value.extra.source_text_word_count === "28",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units: 165,
+          source_text_word_count: 28,
+        },
       }
     );
 
@@ -166,16 +166,16 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 4,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "fa",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.source_text_code_units === "165",
-          value => value.extra.source_text_word_count === "28",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "fa",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units: 165,
+          source_text_word_count: 28,
+        },
       }
     );
 
@@ -204,14 +204,14 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 5,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "fa",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "full-page",
-          value => value.extra.auto_translate === "false",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "fa",
+          top_preferred_language: "en",
+          request_target: "full-page",
+          auto_translate: false,
+        },
       }
     );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_select_telemetry_settings_menu.js b/browser/components/translations/tests/browser/browser_translations_select_telemetry_settings_menu.js
index 7cbbd11f9adf..4a9889365045 100644
--- a/browser/components/translations/tests/browser/browser_translations_select_telemetry_settings_menu.js
+++ b/browser/components/translations/tests/browser/browser_translations_select_telemetry_settings_menu.js
@@ -28,28 +28,28 @@ add_task(
       {
         expectedEventCount: 1,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value => value.extra.source_text_code_units == "56",
-          value => value.extra.source_text_word_count === "9",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units: 56,
+          source_text_word_count: 9,
+        },
       }
     );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_select_telemetry_translation_failure_ui.js b/browser/components/translations/tests/browser/browser_translations_select_telemetry_translation_failure_ui.js
index 7c840488e3c4..359018d06d5d 100644
--- a/browser/components/translations/tests/browser/browser_translations_select_telemetry_translation_failure_ui.js
+++ b/browser/components/translations/tests/browser/browser_translations_select_telemetry_translation_failure_ui.js
@@ -30,42 +30,41 @@ add_task(
       {
         expectedEventCount: 1,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "1616" // With carriage returns
-              : "1607"), // No carriage returns
-          value => value.extra.source_text_word_count === "257",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 1616 // With carriage returns
+              : 1607, // No carriage returns
+          source_text_word_count: 257,
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsSelectTranslationsPanel.translationFailureMessage,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          from_language: "fr",
+          to_language: "en",
+        },
       }
     );
 
@@ -84,30 +83,29 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 2,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "1616" // With carriage returns
-              : "1607"), // No carriage returns
-          value => value.extra.source_text_word_count === "257",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 1616 // With carriage returns
+              : 1607, // No carriage returns
+          source_text_word_count: 257,
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsSelectTranslationsPanel.translationFailureMessage,
       {
         expectedEventCount: 2,
-        finalValuePredicates: [
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          from_language: "fr",
+          to_language: "en",
+        },
       }
     );
 
@@ -139,42 +137,41 @@ add_task(
       {
         expectedEventCount: 2,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 3,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "1616" // With carriage returns
-              : "1607"), // No carriage returns
-          value => value.extra.source_text_word_count === "257",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 1616 // With carriage returns
+              : 1607, // No carriage returns
+          source_text_word_count: 257,
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsSelectTranslationsPanel.translationFailureMessage,
       {
         expectedEventCount: 3,
-        finalValuePredicates: [
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          from_language: "fr",
+          to_language: "en",
+        },
       }
     );
 
@@ -192,20 +189,19 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 4,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "1616" // With carriage returns
-              : "1607"), // No carriage returns
-          value => value.extra.source_text_word_count === "257",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 1616 // With carriage returns
+              : 1607, // No carriage returns
+          source_text_word_count: 257,
+        },
       }
     );
 
diff --git a/browser/components/translations/tests/browser/browser_translations_select_telemetry_unsupported_language_ui.js b/browser/components/translations/tests/browser/browser_translations_select_telemetry_unsupported_language_ui.js
index 06edb10e5af5..f0ad3efdd91c 100644
--- a/browser/components/translations/tests/browser/browser_translations_select_telemetry_unsupported_language_ui.js
+++ b/browser/components/translations/tests/browser/browser_translations_select_telemetry_unsupported_language_ui.js
@@ -30,22 +30,22 @@ add_task(
       {
         expectedEventCount: 1,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsSelectTranslationsPanel.unsupportedLanguageMessage,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.detected_language === "es",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          detected_language: "es",
+        },
       }
     );
 
@@ -73,22 +73,22 @@ add_task(
       {
         expectedEventCount: 2,
         expectNewFlowId: true,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "es",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "es",
+          to_language: "en",
+          top_preferred_language: "en",
+        },
       }
     );
     await TestTranslationsTelemetry.assertEvent(
       Glean.translationsSelectTranslationsPanel.unsupportedLanguageMessage,
       {
         expectedEventCount: 2,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.detected_language === "es",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          detected_language: "es",
+        },
       }
     );
 
@@ -109,20 +109,19 @@ add_task(
       Glean.translations.translationRequest,
       {
         expectedEventCount: 1,
-        finalValuePredicates: [
-          value => value.extra.document_language === "es",
-          value => value.extra.from_language === "fr",
-          value => value.extra.to_language === "en",
-          value => value.extra.top_preferred_language === "en",
-          value => value.extra.request_target === "select",
-          value => value.extra.auto_translate === "false",
-          value =>
-            value.extra.source_text_code_units ===
-            (AppConstants.platform === "win"
-              ? "2064" // With carriage returns
-              : "2041"), // No carriage returns
-          value => value.extra.source_text_word_count === "358",
-        ],
+        assertForMostRecentEvent: {
+          document_language: "es",
+          from_language: "fr",
+          to_language: "en",
+          top_preferred_language: "en",
+          request_target: "select",
+          auto_translate: false,
+          source_text_code_units:
+            AppConstants.platform === "win"
+              ? 2064 // With carriage returns
+              : 2041, // No carriage returns
+          source_text_word_count: 358,
+        },
       }
     );
 
diff --git a/toolkit/components/translations/tests/browser/shared-head.js b/toolkit/components/translations/tests/browser/shared-head.js
index 5ebea7da4b09..66152600ac46 100644
--- a/toolkit/components/translations/tests/browser/shared-head.js
+++ b/toolkit/components/translations/tests/browser/shared-head.js
@@ -1215,18 +1215,18 @@ class TestTranslationsTelemetry {
    * @param {object} expectations - The test expectations.
    * @param {number} expectations.expectedEventCount - The expected count of events.
    * @param {boolean} expectations.expectNewFlowId
-   * @param {Array<Function>} [expectations.allValuePredicates=[]]
-   * - An array of function predicates to assert for all event values.
-   * @param {Array<Function>} [expectations.finalValuePredicates=[]]
-   * - An array of function predicates to assert for only the final event value.
+   * @param {Record<string, string | boolean | number>} [expectations.assertForAllEvents]
+   * - A record of key-value pairs to assert against all events in this category.
+   * @param {Record<string, string | boolean | number>} [expectations.assertForMostRecentEvent]
+   * - A record of key-value pairs to assert against the most recently recorded event in this category.
    */
   static async assertEvent(
     event,
     {
       expectedEventCount,
       expectNewFlowId = null,
-      allValuePredicates = [],
-      finalValuePredicates = [],
+      assertForAllEvents = {},
+      assertForMostRecentEvent = {},
     }
   ) {
     // Ensures that glean metrics are collected from all child processes
@@ -1277,34 +1277,38 @@ class TestTranslationsTelemetry {
       `There should be ${expectedEventCount} telemetry events of type ${name}`
     );
 
-    if (allValuePredicates.length !== 0) {
+    if (Object.keys(assertForAllEvents).length !== 0) {
       is(
         eventCount > 0,
         true,
-        `Telemetry event ${name} should contain values if allPredicates are specified`
+        `Telemetry event ${name} should contain values if assertForMostRecentEvent are specified`
       );
-      for (const value of events) {
-        for (const predicate of allValuePredicates) {
+      for (const [key, expectedEntry] of Object.entries(
+        assertForMostRecentEvent
+      )) {
+        for (const event of events) {
           is(
-            predicate(value),
-            true,
-            `Telemetry event ${name} allPredicate { ${predicate.toString()} } should pass for each value`
+            event.extra[key],
+            String(expectedEntry),
+            `Telemetry event ${name} value for ${key} should match the expected entry`
           );
         }
       }
     }
 
-    if (finalValuePredicates.length !== 0) {
+    if (Object.keys(assertForMostRecentEvent).length !== 0) {
       is(
         eventCount > 0,
         true,
-        `Telemetry event ${name} should contain values if finalPredicates are specified`
+        `Telemetry event ${name} should contain values if assertForMostRecentEvent are specified`
       );
-      for (const predicate of finalValuePredicates) {
+      for (const [key, expectedEntry] of Object.entries(
+        assertForMostRecentEvent
+      )) {
         is(
-          predicate(events[eventCount - 1]),
-          true,
-          `Telemetry event ${name} finalPredicate { ${predicate.toString()} } should pass for final value`
+          events[eventCount - 1].extra[key],
+          String(expectedEntry),
+          `Telemetry event ${name} value for ${key} should match the expected entry`
         );
       }
     }