[ggj][gapic][1/5] feat: add new unit test for testing file-diff infra

src/test/java/com/google/api/generator/gapic/BUILD.bazel

@@ -4,6 +4,7 @@ filegroup(
     name = "gapic_files",
     srcs = [
         "//src/test/java/com/google/api/generator/gapic/composer:composer_files",
+        "//src/test/java/com/google/api/generator/gapic/dummy:dummy_files",
         "//src/test/java/com/google/api/generator/gapic/model:model_files",
         "//src/test/java/com/google/api/generator/gapic/protoparser:protoparser_files",
     ],

src/test/java/com/google/api/generator/gapic/dummy/BUILD.bazel

@@ -0,0 +1,21 @@
+package(default_visibility = ["//visibility:public"])
+
+TESTS = [
+    "FileDiffInfraDummyTest",
+]
+
+filegroup(
+    name = "dummy_files",
+    srcs = ["{0}.java".format(f) for f in TESTS],
+)
+
+[java_test(
+    name = test_name,
+    srcs = ["{0}.java".format(test_name)],
+    test_class = "com.google.api.generator.gapic.dummy.{0}".format(test_name),
+    deps = [
+        "//src/main/java/com/google/api/generator/engine/ast",
+        "//src/main/java/com/google/api/generator/engine/writer",
+        "@junit_junit//jar",
+    ],
+) for test_name in TESTS]

src/test/java/com/google/api/generator/gapic/dummy/FileDiffInfraDummyTest.java

@@ -0,0 +1,104 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//      http://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 com.google.api.generator.gapic.dummy;
+
+import static junit.framework.Assert.assertEquals;
+
+import com.google.api.generator.engine.ast.BlockComment;
+import com.google.api.generator.engine.ast.ClassDefinition;
+import com.google.api.generator.engine.ast.CommentStatement;
+import com.google.api.generator.engine.ast.LineComment;
+import com.google.api.generator.engine.ast.ScopeNode;
+import com.google.api.generator.engine.writer.JavaWriterVisitor;
+import java.util.Arrays;
+import org.junit.Test;
+
+public class FileDiffInfraDummyTest {
+  // Add two simple tests for testing the file-diff infra.
+  // 1. The two unit tests create simple java classes.
+  // 2. Two unit tests are created because we have the case of two expected strings comparison
+  // in one test class e.g. ResourceNameHelperClassComposer. In that case, two golden files will be
+  // created.
+  //
+  // TODO(xiaozhenliu): remove this test class once the file-diff infra is in place and well-tested.
+  @Test
+  public void simpleClass() {
+    ClassDefinition classDef =
+        ClassDefinition.builder()
+            .setHeaderCommentStatements(
+                Arrays.asList(
+                    CommentStatement.withComment(
+                        LineComment.withComment("This is a test class for file-diff infra"))))
+            .setPackageString("com.google.showcase.v1beta1.stub")
+            .setName("EchoStubSettings")
+            .setScope(ScopeNode.PUBLIC)
+            .build();
+    JavaWriterVisitor visitor = new JavaWriterVisitor();
+    classDef.accept(visitor);
+    assertEquals(visitor.write(), EXPECTED_CLASS_STRING_SIMPLE);
+  }
+
+  @Test
+  public void classWithHeader() {
+    ClassDefinition classDef =
+        ClassDefinition.builder()
+            .setFileHeader(
+                Arrays.asList(
+                    CommentStatement.withComment(BlockComment.withComment(APACHE_LICENSE_STRING))))
+            .setPackageString("com.google.showcase.v1beta1.stub")
+            .setName("EchoStubSettings")
+            .setScope(ScopeNode.PUBLIC)
+            .build();
+    JavaWriterVisitor visitor = new JavaWriterVisitor();
+    classDef.accept(visitor);
+    assertEquals(visitor.write(), EXPECTED_CLASS_STRING_WITH_HEADER);
+  }
+
+  private static final String APACHE_LICENSE_STRING =
+      "Copyright 2020 Google LLC\n\n"
+          + "Licensed under the Apache License, Version 2.0 (the \"License\");\n"
+          + "you may not use this file except in compliance with the License.\n"
+          + "You may obtain a copy of the License at\n\n"
+          + "     https://www.apache.org/licenses/LICENSE-2.0\n\n"
+          + "Unless required by applicable law or agreed to in writing, software\n"
+          + "distributed under the License is distributed on an \"AS IS\" BASIS,\n"
+          + "WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
+          + "See the License for the specific language governing permissions and\n"
+          + "limitations under the License.";
+
+  private static final String EXPECTED_CLASS_STRING_SIMPLE =
+      "package com.google.showcase.v1beta1.stub;\n\n"
+          + "// This is a test class for file-diff infra\n"
+          + "public class EchoStubSettings {}\n";
+
+  private static final String EXPECTED_CLASS_STRING_WITH_HEADER =
+      "/*\n"
+          + " * Copyright 2020 Google LLC\n"
+          + " *\n"
+          + " * Licensed under the Apache License, Version 2.0 (the \"License\");\n"
+          + " * you may not use this file except in compliance with the License.\n"
+          + " * You may obtain a copy of the License at\n"
+          + " *\n"
+          + " *      https://www.apache.org/licenses/LICENSE-2.0\n"
+          + " *\n"
+          + " * Unless required by applicable law or agreed to in writing, software\n"
+          + " * distributed under the License is distributed on an \"AS IS\" BASIS,\n"
+          + " * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
+          + " * See the License for the specific language governing permissions and\n"
+          + " * limitations under the License.\n"
+          + " */\n\n"
+          + "package com.google.showcase.v1beta1.stub;\n\n"
+          + "public class EchoStubSettings {}\n";
+}

src/test/java/com/google/api/generator/gapic/dummy/goldens/BUILD.bazel

@@ -0,0 +1,6 @@
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "goldens_files",
+    srcs = glob(["*.golden"]),
+)

src/test/java/com/google/api/generator/gapic/dummy/goldens/FileDiffInfraDummyTestClassWithHeader.golden

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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 com.google.showcase.v1beta1.stub;
+
+public class EchoStubSettings {}

src/test/java/com/google/api/generator/gapic/dummy/goldens/FileDiffInfraDummyTestSimpleClass.golden

@@ -0,0 +1,4 @@
+package com.google.showcase.v1beta1.stub;
+
+// This is a test class for file-diff infra
+public class EchoStubSettings {}