BC support for some PHPUnit 6 versions.

Author: SpacePossum

src/Differ.php

@@ -23,9 +23,26 @@ final class Differ
      */
     private $outputBuilder;
 
-    public function __construct(DiffOutputBuilderInterface $outputBuilder = null)
+    /**
+     * @param DiffOutputBuilderInterface $outputBuilder
+     */
+    public function __construct($outputBuilder = null)
     {
-        $this->outputBuilder = $outputBuilder ?? new UnifiedDiffOutputBuilder();
+        if ($outputBuilder instanceof DiffOutputBuilderInterface) {
+            $this->outputBuilder = $outputBuilder;
+        } elseif (null === $outputBuilder) {
+            $this->outputBuilder = new UnifiedDiffOutputBuilder();
+        } elseif (\is_string($outputBuilder)) {
+            // PHPUnit 6.1.4, 6.2.0, 6.2.1, 6.2.2, and 6.2.3 support
+            // @ see https://github.com/sebastianbergmann/phpunit/issues/2734#issuecomment-314514056
+            // @ deprecated
+            $this->outputBuilder = new UnifiedDiffOutputBuilder($outputBuilder);
+        } else {
+            throw new \InvalidArgumentException(\sprintf(
+                'Expected builder to be an instance of DiffOutputBuilderInterface, <null> or a string, got %s.',
+                \is_object($outputBuilder) ? 'instance of "' . \get_class($outputBuilder) . '"' : \gettype($outputBuilder) . ' "' . $outputBuilder . '"'
+            ));
+        }
     }
 
     /**

tests/DifferTest.php

@@ -1005,4 +1005,40 @@ public function provideDiffWithLineNumbers(): array
             ],
         ];
     }
+
+    public function testConstructorNull()
+    {
+        $diff       = new Differ(null);
+        $reflection = new \ReflectionObject($diff);
+        $property   = $reflection->getProperty('outputBuilder');
+        $property->setAccessible(true);
+
+        $this->assertInstanceOf(UnifiedDiffOutputBuilder::class, $property->getValue($diff));
+    }
+
+    public function testConstructorString()
+    {
+        $diff       = new Differ("--- Original\n+++ New\n");
+        $reflection = new \ReflectionObject($diff);
+        $property   = $reflection->getProperty('outputBuilder');
+        $property->setAccessible(true);
+
+        $this->assertInstanceOf(UnifiedDiffOutputBuilder::class, $property->getValue($diff));
+    }
+
+    public function testConstructorInvalidArgInt()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessageRegExp('/^Expected builder to be an instance of DiffOutputBuilderInterface, <null> or a string, got integer "1"\.$/');
+
+        new Differ(1);
+    }
+
+    public function testConstructorInvalidArgObject()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessageRegExp('/^Expected builder to be an instance of DiffOutputBuilderInterface, <null> or a string, got instance of "SplFileInfo"\.$/');
+
+        new Differ(new \SplFileInfo(__FILE__));
+    }
 }