RuleTestCase: improve main assert error message

src/RuleTestCase.php

@@ -14,6 +14,7 @@
 use function file_get_contents;
 use function file_put_contents;
 use function implode;
+use function in_array;
 use function ksort;
 use function preg_match;
 use function preg_match_all;
@@ -62,10 +63,15 @@ protected function analyzeFiles(
             $actualErrors = $this->processActualErrors(array_values($fileErrors));
             $expectedErrors = $this->parseExpectedErrors($file);
 
+            $extraErrors = array_filter($actualErrors, static fn (string $error): bool => !in_array($error, $expectedErrors, true));
+            $missingErrors = array_filter($expectedErrors, static fn (string $error): bool => !in_array($error, $actualErrors, true));
+
             self::assertSame(
                 implode("\n", $expectedErrors) . "\n",
                 implode("\n", $actualErrors) . "\n",
-                "Errors in file {$file} do not match",
+                "Errors in file {$file} do not match:\n\n" .
+                ($extraErrors === [] ? '' : "New errors reported:\n" . implode("\n", $extraErrors) . "\n\n") .
+                ($missingErrors === [] ? '' : "Errors not reported:\n" . implode("\n", $missingErrors) . "\n\n"),
             );
         }
     }

tests/Rule/Data/DisallowDivisionByLiteralZeroRule/error-message.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace DisallowDivisionByLiteralZeroRule;
+
+function testErrorMessage(): void
+{
+    $a = 10;
+    $invalidDivision = $a / 0; // error: This error should not be reported
+    $validDivision = $a / 2; // error: Division by literal zero is not allowed
+}

tests/RuleTestCaseTest.php

@@ -53,4 +53,28 @@ public function testAutofix(): void
         self::assertFileEquals($expectedFile, $tmpFile);
     }
 
+    public function testErrorMessageFormat(): void
+    {
+        $testFile = str_replace('/', DIRECTORY_SEPARATOR, __DIR__ . '/Rule/Data/DisallowDivisionByLiteralZeroRule/error-message.php');
+
+        try {
+            $this->analyzeFiles([$testFile]);
+            self::fail('Expected assertion to fail');
+        } catch (AssertionFailedError $e) { // @phpstan-ignore catch.internalClass
+            $expectedMessage = <<<MSG
+                Errors in file {$testFile} do not match:
+
+                New errors reported:
+                08: Division by literal zero is not allowed
+
+                Errors not reported:
+                08: This error should not be reported
+                09: Division by literal zero is not allowed
+
+
+                MSG;
+            self::assertStringContainsString($expectedMessage, $e->getMessage());
+        }
+    }
+
 }