Add tracingServiceMock test util

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

.changeset/backend-test-utils-tracing-service-mock.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-test-utils': patch
+---
+
+Added a new tracing service mock to be leveraged in tests

packages/backend-test-utils/report-alpha.api.md

@@ -14,6 +14,10 @@ import { JsonValue } from '@backstage/types';
 import { LoggerService } from '@backstage/backend-plugin-api';
 import { MetricsService } from '@backstage/backend-plugin-api/alpha';
 import { ServiceFactory } from '@backstage/backend-plugin-api';
+import { TracingService } from '@backstage/backend-plugin-api/alpha';
+import { TracingServiceAttributeValue } from '@backstage/backend-plugin-api/alpha';
+import { TracingServiceSpan } from '@backstage/backend-plugin-api/alpha';
+import { TracingServiceSpanStatus } from '@backstage/backend-plugin-api/alpha';
 
 // @alpha (undocumented)
 export function actionsRegistryServiceMock(options?: {
@@ -81,6 +85,14 @@ export class MockActionsRegistry
   >(options: ActionsRegistryActionOptions<TInputSchema, TOutputSchema>): void;
 }
 
+// @alpha
+export interface MockedTracingServiceSpan extends TracingServiceSpan {
+  // (undocumented)
+  setAttribute: jest.Mock<void, [string, TracingServiceAttributeValue]>;
+  // (undocumented)
+  setStatus: jest.Mock<void, [TracingServiceSpanStatus]>;
+}
+
 // @public (undocumented)
 export type ServiceMock<TService> = {
   factory: ServiceFactory<TService>;
@@ -92,5 +104,20 @@ export type ServiceMock<TService> = {
     : TService[Key];
 };
 
+// @alpha
+export interface TracingServiceMock extends TracingService {
+  // (undocumented)
+  factory: ServiceFactory<TracingService>;
+  spans: MockedTracingServiceSpan[];
+  // (undocumented)
+  startActiveSpan: jest.MockedFunction<TracingService['startActiveSpan']>;
+}
+
+// @alpha (undocumented)
+export namespace tracingServiceMock {
+  const factory: () => ServiceFactory<TracingService, 'plugin', 'singleton'>;
+  const mock: () => TracingServiceMock;
+}
+
 // (No @packageDocumentation comment for this package)
 ```

packages/backend-test-utils/src/alpha/services/TracingServiceMock.ts

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2026 The Backstage 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.
+ */
+
+import {
+  createServiceFactory,
+  ServiceFactory,
+} from '@backstage/backend-plugin-api';
+import {
+  TracingService,
+  TracingServiceAttributeValue,
+  TracingServiceSpan,
+  TracingServiceSpanStatus,
+  tracingServiceRef,
+} from '@backstage/backend-plugin-api/alpha';
+import { tracingServiceFactory } from '@backstage/backend-defaults/alpha';
+
+/**
+ * A jest-mocked span captured by {@link TracingServiceMock}.
+ *
+ * @alpha
+ */
+export interface MockedTracingServiceSpan extends TracingServiceSpan {
+  setAttribute: jest.Mock<void, [string, TracingServiceAttributeValue]>;
+  setStatus: jest.Mock<void, [TracingServiceSpanStatus]>;
+}
+
+/**
+ * Mock for the `TracingService`. Captures every span created via
+ * `startActiveSpan` so tests can assert on the options passed in and the
+ * methods called on the span inside the callback.
+ *
+ * @alpha
+ */
+export interface TracingServiceMock extends TracingService {
+  startActiveSpan: jest.MockedFunction<TracingService['startActiveSpan']>;
+  /** Spans created by `startActiveSpan` calls, in order. */
+  spans: MockedTracingServiceSpan[];
+  factory: ServiceFactory<TracingService>;
+}
+
+/**
+ * @alpha
+ */
+export namespace tracingServiceMock {
+  /**
+   * Returns the real `tracingServiceFactory` from `@backstage/backend-defaults`,
+   * for tests that want the full default implementation.
+   */
+  export const factory = () => tracingServiceFactory;
+
+  /**
+   * Builds a mock `TracingService` backed by jest mocks.
+   */
+  export const mock = (): TracingServiceMock => {
+    const spans: MockedTracingServiceSpan[] = [];
+    const startActiveSpan = jest.fn(async (_name, fn, _options) => {
+      const span: MockedTracingServiceSpan = {
+        setAttribute: jest.fn(),
+        setStatus: jest.fn(),
+      };
+      spans.push(span);
+      return await fn(span);
+    }) as TracingServiceMock['startActiveSpan'];
+
+    const service: TracingService = { startActiveSpan };
+
+    return Object.assign(service as TracingServiceMock, {
+      spans,
+      factory: createServiceFactory({
+        service: tracingServiceRef,
+        deps: {},
+        factory: () => service,
+      }),
+    });
+  };
+}

packages/backend-test-utils/src/alpha/services/index.ts

@@ -18,4 +18,9 @@ export { actionsRegistryServiceMock } from './ActionsRegistryServiceMock';
 export { MockActionsRegistry } from './MockActionsRegistry';
 export { actionsServiceMock } from './ActionsServiceMock';
 export { metricsServiceMock } from './MetricsServiceMock';
+export {
+  tracingServiceMock,
+  type TracingServiceMock,
+  type MockedTracingServiceSpan,
+} from './TracingServiceMock';
 export { type ServiceMock } from './alphaCreateServiceMock';

packages/backend-test-utils/src/wiring/TestBackend.ts

@@ -44,6 +44,7 @@ import {
   actionsRegistryServiceMock,
   actionsServiceMock,
   metricsServiceMock,
+  tracingServiceMock,
 } from '../alpha/services';
 
 /** @public */
@@ -94,6 +95,7 @@ export const defaultServiceFactories = [
   actionsRegistryServiceMock.factory(),
   actionsServiceMock.factory(),
   metricsServiceMock.factory(),
+  tracingServiceMock.factory(),
 ];
 
 /**