[SDK][Trace] Add tests for default id generator (#4043)

Signed-off-by: Chen Xu <chen.x@uber.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

sdk/trace/id_generator_test.go

@@ -0,0 +1,52 @@
+// 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 trace
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"go.opentelemetry.io/otel/trace"
+)
+
+func TestNewIDs(t *testing.T) {
+	gen := defaultIDGenerator()
+	n := 1000
+
+	for i := 0; i < n; i++ {
+		traceID, spanID := gen.NewIDs(context.Background())
+		assert.Truef(t, traceID.IsValid(), "trace id: %s", traceID.String())
+		assert.Truef(t, spanID.IsValid(), "span id: %s", spanID.String())
+	}
+}
+
+func TestNewSpanID(t *testing.T) {
+	gen := defaultIDGenerator()
+	testTraceID := [16]byte{123, 123}
+	n := 1000
+
+	for i := 0; i < n; i++ {
+		spanID := gen.NewSpanID(context.Background(), testTraceID)
+		assert.Truef(t, spanID.IsValid(), "span id: %s", spanID.String())
+	}
+}
+
+func TestNewSpanIDWithInvalidTraceID(t *testing.T) {
+	gen := defaultIDGenerator()
+	spanID := gen.NewSpanID(context.Background(), trace.TraceID{})
+	assert.Truef(t, spanID.IsValid(), "span id: %s", spanID.String())
+}