Add exception testing to Python

src/main/java/com/google/api/codegen/transformer/py/PythonImportSectionTransformer.java

@@ -48,10 +48,11 @@ public ImportSectionView generateImportSection(
   }
 
   public ImportSectionView generateTestImportSection(SurfaceTransformerContext context) {
-    ImportSectionView.Builder importSection = ImportSectionView.newBuilder();
-    importSection.standardImports(generateTestStandardImports());
-    importSection.appImports(generateTestAppImports(context));
-    return importSection.build();
+    return ImportSectionView.newBuilder()
+        .standardImports(generateTestStandardImports())
+        .externalImports(generateTestExternalImports())
+        .appImports(generateTestAppImports(context))
+        .build();
   }
 
   private List<ImportFileView> generateInitCodeAppImports(
@@ -109,6 +110,10 @@ private List<ImportFileView> generateTestStandardImports() {
     return ImmutableList.of(createImport("mock"), createImport("unittest2"));
   }
 
+  private List<ImportFileView> generateTestExternalImports() {
+    return ImmutableList.of(createImport("google.gax", "errors"));
+  }
+
   private List<ImportFileView> generateTestAppImports(SurfaceTransformerContext context) {
     Set<ImportFileView> appImports = new TreeSet<>(importFileViewComparator());
     for (Map.Entry<String, TypeAlias> entry : context.getTypeTable().getImports().entrySet()) {

src/main/java/com/google/api/codegen/transformer/py/PythonSurfaceNamer.java

@@ -100,6 +100,13 @@ public String getTestCaseName(SymbolTable symbolTable, Method method) {
     return publicMethodName(testCaseName);
   }
 
+  @Override
+  public String getExceptionTestCaseName(SymbolTable symbolTable, Method method) {
+    Name testCaseName =
+        symbolTable.getNewSymbol(Name.upperCamel("Test", method.getSimpleName(), "Exception"));
+    return publicMethodName(testCaseName);
+  }
+
   @Override
   public String quoted(String text) {
     return "'" + text + "'";

src/main/resources/com/google/api/codegen/py/test.snip

@@ -2,10 +2,7 @@
 @extends "py/method_sample.snip"
 
 @snippet generate(apiTest)
-    {@licenseSection(apiTest.fileHeader)}
-
-    {@moduleDocstring()}
-    {@renderImportSection(apiTest.fileHeader.importSection)}
+    {@header(apiTest.fileHeader)}
 
     class {@apiTest.testClass.name}(unittest2.TestCase):
 
@@ -15,6 +12,17 @@
         @end
 @end
 
+@private header(fileHeader)
+    {@licenseSection(fileHeader)}
+
+    {@moduleDocstring()}
+    {@renderImportSection(fileHeader.importSection)}
+
+    class CustomException(Exception):
+        pass
+
+@end
+
 @private licenseSection(fileHeader)
     @join line : fileHeader.copyrightLines
         @# {@line}
@@ -57,40 +65,68 @@
 @end
 
 @private nonStreamingOptionalArrayTestCase(test, moduleName)
+    @switch test.clientMethodType
+    @case "OptionalArrayMethod"
+        {@simpleTestCase(test, moduleName)}
+    @default
+        {@unhandledCase()}
+    @end
+@end
+
+@private simpleTestCase(test, moduleName)
     @@mock.patch('google.gax.config.create_stub')
     def {@test.name}(self, mock_create_stub):
-        @switch test.clientMethodType
-        @case "OptionalArrayMethod"
-            {@simpleTestCase(test, moduleName)}
-        @default
-            {@unhandledCase()}
+        @# Mock gRPC layer
+        grpc_stub = mock.Mock()
+        mock_create_stub.return_value = grpc_stub
+
+        client = {@moduleName}.{@test.serviceConstructorName}()
+
+        @if test.hasRequestParameters
+            @# Mock request
+            {@initCode(test.initCode)}
+
+        @end
+        @if test.hasReturnValue
+            @# Mock response
+            {@initCode(test.mockResponse.initCode)}
+            grpc_stub.{@test.grpcStubCallString}.return_value = expected_response
+
+            response = client.{@test.clientMethodName}(\
+                {@fieldSettingArgList(test.initCode.fieldSettings)})
+            self.assertEqual(expected_response, response)
+        @else
+            client.{@test.clientMethodName}(\
+                {@fieldSettingArgList(test.initCode.fieldSettings)})
         @end
-@end
 
-@private simpleTestCase(test, moduleName)
-    @# Mock gRPC layer
-    grpc_stub = mock.Mock()
-    mock_create_stub.return_value = grpc_stub
+        grpc_stub.{@test.grpcStubCallString}.assert_called_once()
 
-    client = {@moduleName}.{@test.serviceConstructorName}()
+    @@mock.patch('google.gax.config.API_ERRORS', (CustomException,))
+    @@mock.patch('google.gax.config.create_stub')
+    def {@test.nameWithException}(self, mock_create_stub):
+        @# Mock gRPC layer
+        grpc_stub = mock.Mock()
+        mock_create_stub.return_value = grpc_stub
 
-    @if test.hasRequestParameters
-        @# Mock request
-        {@initCode(test.initCode)}
+        client = {@moduleName}.{@test.serviceConstructorName}()
 
-    @end
-    @if test.hasReturnValue
-        @# Mock response
-        {@initCode(test.mockResponse.initCode)}
-        grpc_stub.{@test.grpcStubCallString}.return_value = expected_response
-
-        response = client.{@test.clientMethodName}(\
-            {@fieldSettingArgList(test.initCode.fieldSettings)})
-        self.assertEqual(expected_response, response)
-    @else
-        client.{@test.clientMethodName}(\
-            {@fieldSettingArgList(test.initCode.fieldSettings)})
-    @end
+        @if test.hasRequestParameters
+            @# Mock request
+            {@initCode(test.initCode)}
+
+        @end
+        @# Mock exception response
+        grpc_stub.{@test.grpcStubCallString}.side_effect = CustomException()
+
+        self.assertRaises(\
+            errors.GaxError, \
+            client.{@test.clientMethodName}\
+            {@fieldSettingArgListAfterComma(test.initCode.fieldSettings)})
+@end
 
-    grpc_stub.{@test.grpcStubCallString}.assert_called_once()
+@private fieldSettingArgListAfterComma(fieldSettings)
+  @if fieldSettings
+    , {@fieldSettingArgList(fieldSettings)}
+  @end
 @end