diff --git a/mypy/test/data.py b/mypy/test/data.py
index 976e68c38a98..bd3dfa6de1c9 100644
--- a/mypy/test/data.py
+++ b/mypy/test/data.py
@@ -208,6 +208,7 @@ def parse_test_case(case: DataDrivenTestCase) -> None:
                 ).format(passnum, case.file, first_item.line)
             )
 
+    output_inline_start = len(output)
     input = first_item.data
     expand_errors(input, output, "main")
     for file_path, contents in files:
@@ -225,6 +226,7 @@ def parse_test_case(case: DataDrivenTestCase) -> None:
 
     case.input = input
     case.output = output
+    case.output_inline_start = output_inline_start
     case.output2 = output2
     case.last_line = case.line + item.line + len(item.data) - 2
     case.files = files
@@ -246,6 +248,7 @@ class DataDrivenTestCase(pytest.Item):
 
     input: list[str]
     output: list[str]  # Output for the first pass
+    output_inline_start: int
     output2: dict[int, list[str]]  # Output for runs 2+, indexed by run number
 
     # full path of test suite
diff --git a/mypy/test/testcheck.py b/mypy/test/testcheck.py
index bdd722c5d6ff..fad70945f740 100644
--- a/mypy/test/testcheck.py
+++ b/mypy/test/testcheck.py
@@ -84,6 +84,19 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
         else:
             self.run_case_once(testcase)
 
+    def _sort_output_if_needed(self, testcase: DataDrivenTestCase, a: list[str]) -> None:
+        idx = testcase.output_inline_start
+        if not testcase.files or idx == len(testcase.output):
+            return
+
+        def _filename(_msg: str) -> str:
+            return _msg.partition(":")[0]
+
+        file_weights = {file: idx for idx, file in enumerate(_filename(msg) for msg in a)}
+        testcase.output[idx:] = sorted(
+            testcase.output[idx:], key=lambda msg: file_weights.get(_filename(msg), -1)
+        )
+
     def run_case_once(
         self,
         testcase: DataDrivenTestCase,
@@ -163,21 +176,20 @@ def run_case_once(
             a = normalize_error_messages(a)
 
         # Make sure error messages match
-        if incremental_step == 0:
-            # Not incremental
-            msg = "Unexpected type checker output ({}, line {})"
+        if incremental_step < 2:
+            if incremental_step == 1:
+                msg = "Unexpected type checker output in incremental, run 1 ({}, line {})"
+            else:
+                assert incremental_step == 0
+                msg = "Unexpected type checker output ({}, line {})"
+            self._sort_output_if_needed(testcase, a)
             output = testcase.output
-        elif incremental_step == 1:
-            msg = "Unexpected type checker output in incremental, run 1 ({}, line {})"
-            output = testcase.output
-        elif incremental_step > 1:
+        else:
             msg = (
                 f"Unexpected type checker output in incremental, run {incremental_step}"
                 + " ({}, line {})"
             )
             output = testcase.output2.get(incremental_step, [])
-        else:
-            raise AssertionError()
 
         if output != a and testcase.config.getoption("--update-data", False):
             update_testcase_output(testcase, a)
diff --git a/test-data/unit/check-basic.test b/test-data/unit/check-basic.test
index c16b9e40122d..e10e69267c5a 100644
--- a/test-data/unit/check-basic.test
+++ b/test-data/unit/check-basic.test
@@ -493,3 +493,13 @@ class A:
 
 [file test.py]
 def foo(s: str) -> None: ...
+
+[case testInlineAssertions]
+import a, b
+s1: str = 42  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
+[file a.py]
+s2: str = 42  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
+[file b.py]
+s3: str = 42  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
+[file c.py]
+s3: str = 'foo'