diff --git a/dlls/kernel32/tests/codepage.c b/dlls/kernel32/tests/codepage.c
index 6e89533076..aa7977d093 100644
--- a/dlls/kernel32/tests/codepage.c
+++ b/dlls/kernel32/tests/codepage.c
@@ -433,6 +433,114 @@ static void test_utf7_encoding(void)
     static const char base64_encoding_table[] =
         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
+    const struct
+    {
+        /* inputs */
+        WCHAR src[16];
+        int srclen;
+        char *dst;
+        int dstlen;
+        /* expected outputs */
+        char expected_dst[16];
+        int chars_written;
+        int len;
+    }
+    tests[] =
+    {
+        /* tests string conversion with srclen=-1 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, sizeof(output) - 1,
+            "+T2BZfVQX-", 11, 11
+        },
+        /* tests string conversion with srclen=-2 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -2, output, sizeof(output) - 1,
+            "+T2BZfVQX-", 11, 11
+        },
+        /* tests string conversion with dstlen=strlen(expected_dst) */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, 10,
+            "+T2BZfVQX-", 10, 0
+        },
+        /* tests string conversion with dstlen=strlen(expected_dst)+1 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, 11,
+            "+T2BZfVQX-", 11, 11
+        },
+        /* tests string conversion with dstlen=strlen(expected_dst)+2 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, 12,
+            "+T2BZfVQX-", 11, 11
+        },
+        /* tests dry run with dst=NULL and dstlen=0 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, NULL, 0,
+            {}, 0, 11
+        },
+        /* tests dry run with dst!=NULL and dstlen=0 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, 0,
+            {}, 0, 11
+        },
+        /* tests srclen < strlenW(src) with directly encodable chars */
+        {
+            {'h','e','l','l','o',0}, 2, output, sizeof(output) - 1,
+            "he", 2, 2
+        },
+        /* tests srclen < strlenW(src) with non-directly encodable chars */
+        {
+            {0x4F60,0x597D,0x5417,0}, 2, output, sizeof(output) - 1,
+            "+T2BZfQ-", 8, 8
+        },
+        /* tests a single null char */
+        {
+            {0}, -1, output, sizeof(output) - 1,
+            "", 1, 1
+        },
+        /* tests a buffer that runs out while not encoding a UTF-7 sequence */
+        {
+            {'h','e','l','l','o',0}, -1, output, 2,
+            "he", 2, 0
+        },
+        /* tests a buffer that runs out after writing 1 base64 character */
+        {
+            {0x4F60,0x0001,0}, -1, output, 2,
+            "+T", 2, 0
+        },
+        /* tests a buffer that runs out after writing 2 base64 characters */
+        {
+            {0x4F60,0x0001,0}, -1, output, 3,
+            "+T2", 3, 0
+        },
+        /* tests a buffer that runs out after writing 3 base64 characters */
+        {
+            {0x4F60,0x0001,0}, -1, output, 4,
+            "+T2A", 4, 0
+        },
+        /* tests a buffer that runs out just after writing the + sign */
+        {
+            {0x4F60,0}, -1, output, 1,
+            "+", 1, 0
+        },
+        /* tests a buffer that runs out just before writing the - sign
+         * the number of bits to encode here is evenly divisible by 6 */
+        {
+            {0x4F60,0x597D,0x5417,0}, -1, output, 9,
+            "+T2BZfVQX", 9, 0
+        },
+        /* tests a buffer that runs out just before writing the - sign
+         * the number of bits to encode here is NOT evenly divisible by 6 */
+        {
+            {0x4F60,0}, -1, output, 4,
+            "+T2", 3, 0
+        },
+        /* tests a buffer that runs out in the middle of escaping a + sign */
+        {
+            {'+',0}, -1, output, 1,
+            "+", 1, 0
+        }
+    };
+
     if (WideCharToMultiByte(CP_UTF7, 0, foobarW, -1, NULL, 0, NULL, NULL) == 0 &&
         GetLastError() == ERROR_CALL_NOT_IMPLEMENTED)
     {
@@ -525,6 +633,34 @@ static void test_utf7_encoding(void)
         ok(output[expected_len] == '#', "i=0x%04x: expected output[%i]='#', got output[%i]=%i\n",
            i, expected_len, expected_len, output[expected_len]);
     }
+
+    for (i = 0; i < sizeof(tests) / sizeof(tests[0]); i++)
+    {
+        memset(output, '#', sizeof(output) - 1);
+        output[sizeof(output) - 1] = 0;
+        SetLastError(0xdeadbeef);
+
+        len = WideCharToMultiByte(CP_UTF7, 0, tests[i].src, tests[i].srclen,
+                                  tests[i].dst, tests[i].dstlen, NULL, NULL);
+
+        if (!tests[i].len)
+        {
+            ok(GetLastError() == ERROR_INSUFFICIENT_BUFFER,
+               "tests[%i]: expected error=0x%x, got error=0x%x\n",
+               i, ERROR_INSUFFICIENT_BUFFER, GetLastError());
+        }
+        ok(len == tests[i].len, "tests[%i]: expected len=%i, got len=%i\n", i, tests[i].len, len);
+
+        if (tests[i].dst)
+        {
+            ok(memcmp(tests[i].dst, tests[i].expected_dst, tests[i].chars_written) == 0,
+               "tests[%i]: expected dst='%s', got dst='%s'\n",
+               i, tests[i].expected_dst, tests[i].dst);
+            ok(tests[i].dst[tests[i].chars_written] == '#',
+               "tests[%i]: expected dst[%i]='#', got dst[%i]=%i\n",
+               i, tests[i].chars_written, tests[i].chars_written, tests[i].dst[tests[i].chars_written]);
+        }
+    }
 }
 
 static void test_utf7_decoding(void)