Fix linting (#1016)

Author: kubawerlos

tests/Fixer/AbstractFixerTestCase.php

@@ -180,6 +180,8 @@ final protected function doTest(string $expected, ?string $input = null, ?array
         $expectedTokens = Tokens::fromCode($expected);
 
         if ($input !== null) {
+            self::assertNull($this->lintSource($input));
+
             Tokens::clearCache();
             $inputTokens = Tokens::fromCode($input);
 
@@ -225,7 +227,7 @@ final protected function lintSource(string $source): ?string
         static $linter;
 
         if ($linter === null) {
-            $linter = \getenv('FAST_LINT_TEST_CASES') !== false ? new Linter() : new ProcessLinter();
+            $linter = \getenv('FAST_LINT_TEST_CASES') === '1' ? new Linter() : new ProcessLinter();
         }
 
         try {

tests/Fixer/NoDuplicatedImportsFixerTest.php

@@ -28,6 +28,9 @@ public function testIsRisky(): void
      */
     public function testFix(string $expected, ?string $input = null): void
     {
+        if (\getenv('FAST_LINT_TEST_CASES') !== '1') {
+            self::markTestSkipped('Duplicated imports can be tested only if FAST_LINT_TEST_CASES is enabled.');
+        }
         $this->doTest($expected, $input);
     }