Allow using env var to disable snapshot creation

Author: mathieutu

src/MatchesSnapshots.php

@@ -142,11 +142,12 @@ protected function shouldUpdateSnapshots(): bool
      * matched.
      *
      * Override this method if you want to use a different flag or mechanism
-     * than `-d --without-creating-snapshots`.
+     * than `-d --without-creating-snapshots` or `CREATE_SNAPSHOTS=false` env var.
      */
     protected function shouldCreateSnapshots(): bool
     {
-        return ! in_array('--without-creating-snapshots', $_SERVER['argv'], true);
+        return ! in_array('--without-creating-snapshots', $_SERVER['argv'], true)
+            && getenv('CREATE_SNAPSHOTS') !== 'false';
     }
 
     protected function doSnapshotAssertion($actual, Driver $driver)
@@ -299,6 +300,7 @@ protected function assertSnapshotShouldBeCreated(string $snapshotFileName): void
         $this->fail(
             "Snapshot \"$snapshotFileName\" does not exist.\n".
             'You can automatically create it by removing '.
+            'the `CREATE_SNAPSHOT=false` env var, or '.
             '`-d --without-creating-snapshots` of PHPUnit\'s CLI arguments.'
         );
     }

tests/Integration/MatchesSnapshotTest.php

@@ -479,7 +479,7 @@ public function it_doesnt_create_a_regular_snapshot_and_mismatches_if_asked()
         $this->expectFail(
             $mockTrait,
             "Snapshot \"MatchesSnapshotTest__it_doesnt_create_a_regular_snapshot_and_mismatches_if_asked__1.txt\" does not exist.\n".
-            'You can automatically create it by removing `-d --without-creating-snapshots` of PHPUnit\'s CLI arguments.'
+            "You can automatically create it by removing the `CREATE_SNAPSHOT=false` env var, or `-d --without-creating-snapshots` of PHPUnit's CLI arguments."
         );
 
         $mockTrait->assertMatchesSnapshot('Bar');
@@ -495,7 +495,39 @@ public function it_doesnt_create_a_file_snapshot_and_mismatches_if_asked()
         $this->expectFail(
             $mockTrait,
             "Snapshot \"MatchesSnapshotTest__it_doesnt_create_a_file_snapshot_and_mismatches_if_asked__1.jpg_failed.jpg\" does not exist.\n".
-            'You can automatically create it by removing `-d --without-creating-snapshots` of PHPUnit\'s CLI arguments.'
+            "You can automatically create it by removing the `CREATE_SNAPSHOT=false` env var, or `-d --without-creating-snapshots` of PHPUnit's CLI arguments."
+        );
+
+        $mockTrait->assertMatchesFileSnapshot(__DIR__.'/stubs/test_files/friendly_man.jpg');
+    }
+
+    /** @test */
+    public function it_doesnt_create_a_regular_snapshot_and_mismatches_if_asked_with_env_var()
+    {
+        putenv('CREATE_SNAPSHOTS=false');
+
+        $mockTrait = $this->getMatchesSnapshotMock();
+
+        $this->expectFail(
+            $mockTrait,
+            "Snapshot \"MatchesSnapshotTest__it_doesnt_create_a_regular_snapshot_and_mismatches_if_asked_with_env_var__1.txt\" does not exist.\n".
+            "You can automatically create it by removing the `CREATE_SNAPSHOT=false` env var, or `-d --without-creating-snapshots` of PHPUnit's CLI arguments."
+        );
+
+        $mockTrait->assertMatchesSnapshot('Bar');
+    }
+
+    /** @test */
+    public function it_doesnt_create_a_file_snapshot_and_mismatches_if_asked_with_env_var()
+    {
+        putenv('CREATE_SNAPSHOT=false');
+
+        $mockTrait = $this->getMatchesSnapshotMock();
+
+        $this->expectFail(
+            $mockTrait,
+            "Snapshot \"MatchesSnapshotTest__it_doesnt_create_a_file_snapshot_and_mismatches_if_asked_with_env_var__1.jpg_failed.jpg\" does not exist.\n".
+            "You can automatically create it by removing the `CREATE_SNAPSHOT=false` env var, or `-d --without-creating-snapshots` of PHPUnit's CLI arguments."
         );
 
         $mockTrait->assertMatchesFileSnapshot(__DIR__.'/stubs/test_files/friendly_man.jpg');