diff --git a/devtools/client/debugger/test/mochitest/browser_dbg-blackbox.js b/devtools/client/debugger/test/mochitest/browser_dbg-blackbox.js
index 8d0d3d62dbaf..3902b2ffad94 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg-blackbox.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg-blackbox.js
@@ -436,8 +436,11 @@ async function testBlackBoxSingleLine(dbg, source) {
   assertNotPaused(dbg);
 
   info("Un-blackbox line 2 of funcA()");
-  selectEditorLines(dbg, 2, 2);
-  await openContextMenuInDebugger(dbg, "CodeMirrorLines");
+  await selectEditorLinesAndOpenContextMenu(
+    dbg,
+    { startLine: 2, endLine: 2 },
+    "CodeMirrorLines"
+  );
   await selectBlackBoxContextMenuItem(dbg, "blackbox-line");
 
   await assertEditorBlackBoxBoxContextMenuItems(dbg, {
@@ -717,16 +720,3 @@ async function assertEditorBlackBoxBoxContextMenuItems(dbg, testFixtures) {
     await closeContextMenu(dbg, popup);
   }
 }
-
-/**
- * Selects a range of lines
- * @param {Object} dbg
- * @param {Number} startLine
- * @param {Number} endLine
- */
-function selectEditorLines(dbg, startLine, endLine) {
-  getCM(dbg).setSelection(
-    { line: startLine - 1, ch: 0 },
-    { line: endLine, ch: 0 }
-  );
-}
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg-console-eval.js b/devtools/client/debugger/test/mochitest/browser_dbg-console-eval.js
index 0e4cf793ecb7..28ebbdb008ca 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg-console-eval.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg-console-eval.js
@@ -15,7 +15,7 @@ add_task(async function () {
   clickElement(dbg, "CodeMirrorLines");
   await waitForElementWithSelector(dbg, ".CodeMirror-code");
 
-  getCM(dbg).setSelection({ line: 0, ch: 0 }, { line: 8, ch: 0 });
+  setSelection(dbg, 1, 7);
 
   rightClickElement(dbg, "CodeMirrorLines");
   await waitForContextMenu(dbg);
diff --git a/devtools/client/debugger/test/mochitest/shared-head.js b/devtools/client/debugger/test/mochitest/shared-head.js
index 0fe66d117b80..1995f3505ac8 100644
--- a/devtools/client/debugger/test/mochitest/shared-head.js
+++ b/devtools/client/debugger/test/mochitest/shared-head.js
@@ -1557,18 +1557,19 @@ async function openContextMenuInDebugger(dbg, elementName, line) {
  * Select a range of lines in the editor and open the contextmenu
  * @param {Object} dbg
  * @param {Object} lines
+ * @param {String} elementName
  * @returns
  */
-async function selectEditorLinesAndOpenContextMenu(dbg, lines) {
+async function selectEditorLinesAndOpenContextMenu(
+  dbg,
+  lines,
+  elementName = "line"
+) {
   const { startLine, endLine } = lines;
-  const elementName = "line";
   if (!endLine) {
     await clickElement(dbg, elementName, startLine);
   } else {
-    getCM(dbg).setSelection(
-      { line: startLine - 1, ch: 0 },
-      { line: endLine, ch: 0 }
-    );
+    setSelection(dbg, startLine, endLine);
   }
   return openContextMenuInDebugger(dbg, elementName, startLine);
 }
@@ -2220,6 +2221,13 @@ function isScrolledPositionVisible(dbg, line, column = 0) {
   line = isCm6Enabled ? line + 1 : line;
   return getCMEditor(dbg).isPositionVisible(line, column);
 }
+     
+function setSelection(dbg, startLine, endLine) {
+  getCMEditor(dbg).setSelectionAt(
+    { line: startLine, column: 0 },
+    { line: endLine, column: 0 }
+  );
+}
 
 // Gets the mode used for the file
 function getEditorFileMode(dbg) {
diff --git a/devtools/client/shared/sourceeditor/editor.js b/devtools/client/shared/sourceeditor/editor.js
index 73b8ec2ebc8f..c5aef08feee6 100644
--- a/devtools/client/shared/sourceeditor/editor.js
+++ b/devtools/client/shared/sourceeditor/editor.js
@@ -3118,6 +3118,24 @@ class Editor extends EventEmitter {
     }
   }
 
+  // Used only in tests
+  setSelectionAt(start, end) {
+    const cm = editors.get(this);
+    if (this.config.cm6) {
+      const from = this.#posToOffset(start.line, start.column);
+      const to = this.#posToOffset(end.line, end.column);
+      if (from == null || to == null) {
+        return;
+      }
+      cm.dispatch({ selection: { anchor: from, head: to } });
+    } else {
+      cm.setSelection(
+        { line: start.line - 1, ch: start.column },
+        { line: end.line - 1, ch: end.column }
+      );
+    }
+  }
+
   // Used only in tests
   setCursorAt(line, column) {
     const cm = editors.get(this);