exception: Add test for MWExceptionHandler trace formatting

Change-Id: I00b9607ba7e17c1f75ef065e83b83d2e1a82870c

tests/common/TestsAutoLoader.php

@@ -33,6 +33,9 @@ $wgAutoloadClasses += [
 	# tests/integration
 	'MWHttpRequestTestCase' => "$testDir/integration/includes/http/MWHttpRequestTestCase.php",
 
+	# tests/exception
+	'TestThrowerDummy' => "$testDir/phpunit/data/exception/TestThrowerDummy.php",
+
 	# tests/parser
 	'DbTestPreviewer' => "$testDir/parser/DbTestPreviewer.php",
 	'DbTestRecorder' => "$testDir/parser/DbTestRecorder.php",

tests/phpunit/data/exception/TestThrowerDummy.php

@@ -0,0 +1,23 @@
+<?php
+
+class TestThrowerDummy {
+	public function main() {
+		$this->doFoo();
+	}
+
+	private function doFoo() {
+		$this->getBar();
+	}
+
+	private function getBar() {
+		$this->getQuux();
+	}
+
+	private function getQuux() {
+		throw new Exception( 'Quux failed' );
+	}
+
+	public static function getFile() : string {
+		return __FILE__;
+	}
+}

tests/phpunit/unit/includes/exception/MWExceptionHandlerTest.php

@@ -22,6 +22,37 @@ class MWExceptionHandlerTest extends \MediaWikiUnitTestCase {
 		parent::tearDown();
 	}
 
+	/**
+	 * Test end-to-end formatting of an exception, such as used by LogstashFormatter.
+	 *
+	 * @covers MWExceptionHandler
+	 * @see MWExceptionHandler::prettyPrintTrace
+	 */
+	public function testTraceFormatting() {
+		try {
+			$dummy = new TestThrowerDummy();
+			$startLine = __LINE__ + 1;
+			$dummy->main();
+		} catch ( Exception $e ) {
+		}
+
+		$startFile = __FILE__;
+		$dummyFile = TestThrowerDummy::getFile();
+		$dummyClass = TestThrowerDummy::class;
+		$expected = <<<TEXT
+#0 ${dummyFile}(13): ${dummyClass}->getQuux()
+#1 ${dummyFile}(9): ${dummyClass}->getBar()
+#2 ${dummyFile}(5): ${dummyClass}->doFoo()
+#3 ${startFile}($startLine): ${dummyClass}->main()
+TEXT;
+
+		// Trim up until our call()
+		$trace = MWExceptionHandler::getRedactedTraceAsString( $e );
+		$actual = implode( "\n", array_slice( explode( "\n", trim( $trace ) ), 0, 4 ) );
+
+		$this->assertEquals( $expected, $actual );
+	}
+
 	/**
 	 * @covers MWExceptionHandler::getRedactedTrace
 	 */