Test that DefaultSubtitleParserFactory format support is consistent

Looping through all MIME types is a bit hacky, but seems like a nice way
to check "all" MIME types (or at least more than a random selection).

PiperOrigin-RevId: 572508027

libraries/extractor/src/test/java/androidx/media3/extractor/text/DefaultSubtitleParserFactoryTest.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package androidx.media3.extractor.text;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import androidx.media3.common.Format;
+import androidx.media3.common.MimeTypes;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.common.base.CharMatcher;
+import com.google.common.collect.ImmutableList;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Tests for {@link DefaultSubtitleParserFactory}. */
+@RunWith(AndroidJUnit4.class)
+public class DefaultSubtitleParserFactoryTest {
+
+  /**
+   * This test loops through all the public fields of {@link MimeTypes} and assumes all the static,
+   * string fields with a single "/" in them are MIME types - then it uses these to 'fuzz' the
+   * {@link DefaultSubtitleParserFactory} to check that, for each MIME type, it either consistently
+   * supports or doesn't support it.
+   */
+  @Test
+  public void formatSupportIsConsistent() throws Exception {
+    DefaultSubtitleParserFactory factory = new DefaultSubtitleParserFactory();
+    for (Field field : MimeTypes.class.getFields()) {
+      if (Modifier.isStatic(field.getModifiers()) && field.getType().equals(String.class)) {
+        String fieldValue = (String) field.get(null);
+        // Filter to only MIME types (values with exactly one '/')
+        if (CharMatcher.is('/').countIn(fieldValue) == 1) {
+          Format.Builder formatBuilder = new Format.Builder().setSampleMimeType(fieldValue);
+          if (fieldValue.equals(MimeTypes.APPLICATION_DVBSUBS)) {
+            formatBuilder.setInitializationData(ImmutableList.of(new byte[] {1, 2, 3, 4}));
+          }
+          Format format = formatBuilder.build();
+          if (factory.supportsFormat(format)) {
+            try {
+              assertThat(factory.getCueReplacementBehavior(format))
+                  .isEqualTo(factory.create(format).getCueReplacementBehavior());
+            } catch (IllegalArgumentException e) {
+              throw new AssertionError(
+                  "Unexpected error for supported MIME type (" + fieldValue + ")", e);
+            }
+          } else {
+            assertThrows(
+                "MIME=" + fieldValue,
+                IllegalArgumentException.class,
+                () -> factory.getCueReplacementBehavior(format));
+            assertThrows(
+                "MIME=" + fieldValue, IllegalArgumentException.class, () -> factory.create(format));
+          }
+        }
+      }
+    }
+  }
+}