Refactor reader testing into a harness (#2910)

* Refactor reader testing into a harness

* Run lint

sdk/metric/manual_reader_test.go

@@ -15,60 +15,9 @@
 package metric // import "go.opentelemetry.io/otel/sdk/metric/reader"
 
 import (
-	"context"
 	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"go.opentelemetry.io/otel/sdk/metric/export"
 )
 
-func TestManualReaderNotRegistered(t *testing.T) {
-	rdr := &manualReader{}
-
-	_, err := rdr.Collect(context.Background())
-	require.ErrorIs(t, err, ErrReaderNotRegistered)
-}
-
-type testProducer struct{}
-
-var testMetrics = export.Metrics{
-	// TODO: test with actual data.
-}
-
-func (p testProducer) produce(context.Context) (export.Metrics, error) {
-	return testMetrics, nil
-}
-
-func TestManualReaderProducer(t *testing.T) {
-	rdr := &manualReader{}
-	rdr.register(testProducer{})
-
-	m, err := rdr.Collect(context.Background())
-	assert.NoError(t, err)
-	assert.Equal(t, testMetrics, m)
-}
-
-func TestManualReaderCollectAfterShutdown(t *testing.T) {
-	rdr := &manualReader{}
-	rdr.register(testProducer{})
-	err := rdr.Shutdown(context.Background())
-	require.NoError(t, err)
-
-	m, err := rdr.Collect(context.Background())
-	assert.ErrorIs(t, err, ErrReaderShutdown)
-	assert.Equal(t, export.Metrics{}, m)
-}
-
-func TestManualReaderShutdown(t *testing.T) {
-	rdr := &manualReader{}
-	rdr.register(testProducer{})
-
-	err := rdr.Shutdown(context.Background())
-	require.NoError(t, err)
-
-	err = rdr.Shutdown(context.Background())
-	assert.ErrorIs(t, err, ErrReaderShutdown)
-
+func TestManualReader(t *testing.T) {
+	testReaderHarness(t, func() Reader { return NewManualReader() })
 }

sdk/metric/reader_test.go

@@ -0,0 +1,92 @@
+// Copyright The OpenTelemetry Authors
+//
+// 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 metric // import "go.opentelemetry.io/otel/sdk/metric/reader"
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/sdk/metric/export"
+)
+
+type readerFactory func() Reader
+
+func testReaderHarness(t *testing.T, f readerFactory) {
+	t.Run("ErrorForNotRegistered", func(t *testing.T) {
+		r := f()
+		ctx := context.Background()
+
+		_, err := r.Collect(ctx)
+		require.ErrorIs(t, err, ErrReaderNotRegistered)
+
+		// Ensure Reader is allowed clean up attempt.
+		_ = r.Shutdown(ctx)
+	})
+
+	t.Run("Producer", func(t *testing.T) {
+		r := f()
+		r.register(testProducer{})
+		ctx := context.Background()
+
+		m, err := r.Collect(ctx)
+		assert.NoError(t, err)
+		assert.Equal(t, testMetrics, m)
+
+		// Ensure Reader is allowed clean up attempt.
+		_ = r.Shutdown(ctx)
+	})
+
+	t.Run("CollectAfterShutdown", func(t *testing.T) {
+		r := f()
+		r.register(testProducer{})
+		require.NoError(t, r.Shutdown(context.Background()))
+
+		m, err := r.Collect(context.Background())
+		assert.ErrorIs(t, err, ErrReaderShutdown)
+		assert.Equal(t, export.Metrics{}, m)
+	})
+
+	t.Run("ShutdownTwice", func(t *testing.T) {
+		r := f()
+		r.register(testProducer{})
+		require.NoError(t, r.Shutdown(context.Background()))
+
+		assert.ErrorIs(t, r.Shutdown(context.Background()), ErrReaderShutdown)
+	})
+
+	t.Run("MultipleForceFlush", func(t *testing.T) {
+		r := f()
+		r.register(testProducer{})
+		ctx := context.Background()
+		require.NoError(t, r.ForceFlush(ctx))
+		assert.NoError(t, r.ForceFlush(ctx))
+
+		// Ensure Reader is allowed clean up attempt.
+		_ = r.Shutdown(ctx)
+	})
+}
+
+var testMetrics = export.Metrics{
+	// TODO: test with actual data.
+}
+
+type testProducer struct{}
+
+func (p testProducer) produce(context.Context) (export.Metrics, error) {
+	return testMetrics, nil
+}