Add an example test, make unified diffs match diff output

Author: fredemmott

src/StringDiff.php

@@ -38,6 +38,12 @@ public function getUnifiedDiff(int $context = 3): string {
     $hunks = vec[];
 
     $remaining = $this->getDiff();
+    $last = C\lastx($remaining);
+    // diff -u ignores trailing newlines
+    if ($last is DiffKeepOp<_> && $last->getContent() === '') {
+      $remaining = Vec\slice($remaining, 0, C\count($remaining) - 1);
+    }
+
     while (!C\is_empty($remaining)) {
       $not_keep = C\find_key($remaining, $row ==> !$row instanceof DiffKeepOp);
       if ($not_keep === null) {

tests/StringDiffTest.php

@@ -30,17 +30,41 @@ public function testDiffLines(): void {
     );
   }
 
-	public function testDiffCharacters(): void {
+  public function testDiffCharacters(): void {
     $diff = StringDiff::characters('abb', 'abc')->getDiff();
-		expect(C\count($diff))->toBeSame(4);
+    expect(C\count($diff))->toBeSame(4);
 
-		expect($diff[0])->toBeInstanceOf(DiffKeepOp::class);
-		expect($diff[1])->toBeInstanceOf(DiffKeepOp::class);
-		expect($diff[2])->toBeInstanceOf(DiffDeleteOp::class);
-		expect($diff[3])->toBeInstanceOf(DiffInsertOp::class);
+    expect($diff[0])->toBeInstanceOf(DiffKeepOp::class);
+    expect($diff[1])->toBeInstanceOf(DiffKeepOp::class);
+    expect($diff[2])->toBeInstanceOf(DiffDeleteOp::class);
+    expect($diff[3])->toBeInstanceOf(DiffInsertOp::class);
+
+    expect(Vec\map($diff, $op ==> $op->getContent()))->toBeSame(
+      vec['a', 'b', 'b', 'c'],
+    );
+  }
+
+  public function provideExamples(): vec<varray<string>> {
+    return Vec\map(
+      \glob(__DIR__.'/examples/*.a'),
+      $ex ==> varray[\basename($ex, '.a')],
+    );
+  }
 
-		expect(Vec\map($diff, $op ==> $op->getContent()))->toBeSame(
-			vec['a', 'b', 'b', 'c'],
-		);
-	}
+  <<DataProvider('provideExamples')>>
+  public function testUnifiedDiff(string $name): void {
+    $base = __DIR__.'/examples/'.$name;
+    $a = \file_get_contents($base.'.a');
+    $b = \file_get_contents($base.'.b');
+    $diff = StringDiff::lines($a, $b)->getUnifiedDiff();
+
+    expect($diff)->toBeSame(
+      \file_get_contents($base.'.udiff.expect'),
+      'Did not match expected contents '.
+      '(from diff -u %s %s | tail -n +3 > %s.udiff.expect)',
+      $base,
+      $base,
+      $base,
+    );
+  }
 }

tests/examples/replace_last.a

@@ -0,0 +1,3 @@
+foo
+bar
+baz

tests/examples/replace_last.b

@@ -0,0 +1,3 @@
+foo
+bar
+herp

tests/examples/replace_last.udiff.expect

@@ -0,0 +1,5 @@
+@@ -1,3 +1,3 @@
+ foo
+ bar
+-baz
++herp