--- sidebar_position: 10 --- # Testing AppKit ships a testing kit at `@databricks/appkit/testing` so you can test a plugin, including its cross-plugin tool calls and streaming responses, without a live Databricks workspace, credentials, or network access. Plugin tests stay fast and run in CI, where no workspace is available. ## Goal Exercise a plugin's real code paths against a real `PluginContext` with only its outer edges faked. That covers route registration, cross-plugin tool dispatch, user-scoped (on-behalf-of) execution, and per-call timeouts. Nothing about the context is reimplemented, so a test can't drift from production behavior. The kit has three entry points plus a set of fixture helpers: - **`createTestApp({ plugins })`** — boot a real app and call it over real HTTP. Start here. - **`createTestPluginContext()`** — build a real `PluginContext` with faked edges and attach it to a plugin, with no boot and no socket. - **`expectStream(...).toEmit(...)`** — assert the ordered event types a stream emits. - **Fixtures** — `createMockRequest`, `createMockResponse`, `createMockWorkspaceClient`, `mockServiceContext`, and SQL response builders. The kit uses [Vitest](https://vitest.dev)'s `vi` for its mocks, so `vitest` is an **optional peer dependency**: you already have it (you're writing Vitest tests), and the kit resolves to your copy rather than bundling a second one. Because it's optional, it is not installed into apps that never import `@databricks/appkit/testing` — production installs stay free of the test framework. Any Vitest v3 or v4 works. ## Testing your plugin `createTestApp({ plugins })` boots a **real** AppKit app, with the real Express wiring, routes, and resource validation, then hands you methods to call it like a client would: ```ts import { createTestApp, expectStream } from "@databricks/appkit/testing"; test("my plugin answers a request", async () => { const app = await createTestApp({ plugins: [myPlugin()] }); try { const res = await app.post("/api/my-plugin/thing", { body: { q: 1 }, obo: true }); expect(res.status).toBe(200); await expectStream(res).toEmit("status", "result"); } finally { await app.close(); } }); ``` No workspace, no credentials, no network. The harness pins a non-development `NODE_ENV`, binds an ephemeral port, installs a fake workspace client, and keeps the cache in memory so nothing reaches out. Paths are the full mounted route. A plugin's prefix is `/api/` plus its manifest name in kebab-case, so a plugin named `mySearch` serves at `/api/my-search/…`. ### Which harness? | | `createTestApp` | `createTestPluginContext` | | --- | --- | --- | | Boots the app | Yes | No | | Binds a socket | Yes (ephemeral port) | No | | Express middleware, error handler | Real | Not involved | | Resource / env validation | Real, and strict | Not involved | | Workspace client | Faked and injected | Fake it yourself with `mockServiceContext` | | Needs `close()` | **Yes** | No | | Speed | Fast, but pays for a socket | Fastest | Use `createTestApp` for a plugin's HTTP behavior end to end. Use `createTestPluginContext` to unit-test wiring: route registration, tool dispatch, timeout composition. Name harness suites `*.integration.test.ts`, matching the existing convention. ### Faking what your plugin reads Declare responses by dotted path — `"."` on AppKit's workspace-client facade: ```ts const app = await createTestApp({ plugins: [myPlugin()], responses: { "jobs.getRun": { state: "TERMINATED", result_state: "SUCCESS" }, "statementExecution.executeStatement": { status: { state: "SUCCEEDED" } }, "apiClient.request": { results: [] }, }, }); ``` A function value receives the call arguments, so you can script per-argument behavior or reject to test an error path. `responses` configures the built-in mock, so passing it alongside your own `client` is rejected rather than silently ignored — configure the responses on that client instead. Any path you **don't** declare resolves `undefined` rather than crashing — see [Mocking Databricks services](#mocking-databricks-services) for the trade-off it makes. For the response *shapes*, follow the service types on the Databricks SDK. The kit doesn't validate them, so a wrong shape fails in your plugin, not in the fake. With one app open, `app.client` is the very object your handler resolves at runtime — reached inside a plugin via `getExecutionContext().client` — so you can assert calls on it: ```ts import { getMock } from "@databricks/appkit/testing"; expect(getMock(app.client, "jobs.getRun")).toHaveBeenCalledWith({ run_id: 42 }); ``` `getMock` exists because facade accessors are typed against the SDK, so `expect(app.client.jobs.getRun).toHaveBeenCalled()` won't typecheck. ### Requests `app.get/post/put/patch/delete(path, options?)` return a native `Response`, so `expectStream` composes directly with no bridge. - `body` — a non-string value is JSON-encoded with `content-type: application/json`. A string is sent as-is. - `headers` — merged last, so they win over anything the harness set. - `obo` — `true` for the default test user, or `{ userId, token, email }`. Same shorthand as `createMockRequest({ obo })`, so a handler using `asUser(req)` resolves that identity. - `signal` — forwarded to `fetch`. ### Teardown The harness binds a socket, so **every boot needs a `close()`**. It releases the socket, runs your plugin's `shutdown()` hooks, drops AppKit's singletons, and restores `process.env` to its pre-boot state. It's idempotent. Prefer `await using`, which closes the app at scope exit even if the test throws: ```ts await using app = await createTestApp({ plugins: [myPlugin()] }); // released at scope exit ``` `try/finally` works too, and is what you need if the app has to outlive a block: ```ts const app = await createTestApp({ plugins: [myPlugin()] }); try { // ... } finally { await app.close(); } ``` Miss the close and the app stays live — socket bound, singletons and `process.env` not restored — so the next `createTestApp` is refused (one app at a time). ### Satisfying declared resources The harness runs the real validator with a strict posture, so a plugin whose manifest requires a resource fails the boot unless its env var is set. Supply it with `env`: ```ts // Throws: MY_WAREHOUSE_ID is required by the manifest. await createTestApp({ plugins: [myPlugin()] }); // Boots. await createTestApp({ plugins: [myPlugin()], env: { MY_WAREHOUSE_ID: "w-1" } }); ``` That makes "my plugin declares its resources correctly" a genuine assertion. `env` is restored on `close()`. :::note What this does not check The harness validates that required resources' **environment variables are present**. It does **not** validate config *values* against your manifest's `config.schema` — no runtime validator exists for that yet. A test that boots successfully tells you your resource declarations and env are wired up; it says nothing about whether your config values are well-formed. ::: ### Other options - `server: false` — no socket. Plugin setup, validation, and teardown still run; the request methods throw if called. Useful when you only care that a plugin boots. - `client` — supply your own workspace client instead of the built-in fake. You then own its `currentUser.me()`: AppKit reads `currentUser.id` during boot and can't start without it. - `nodeEnv` — defaults to `"test"`. `"development"` is **refused**: dev mode routes the harness's ephemeral port through `get-port`, which throws on port `0`, and it also boots a real Vite server and relaxes validation. - `cache` — defaults to in-memory. Overriding it is what would let the cache reach the network, so leave it alone unless that's the point of the test. ## `createTestPluginContext()` `PluginContext` is the mediator AppKit passes to every plugin: it buffers routes, tracks tool providers, and runs cross-plugin tool calls with user scoping and a timeout. `createTestPluginContext()` returns the **real** context with three edges faked: | Edge | How it's faked | | --- | --- | | Telemetry | A no-op mock provider — no OpenTelemetry pipeline needed. | | Tool providers | Fakes registered through the real `registerToolProvider`, keyed by plugin then tool name. | | Routes | The real `addRoute`/`addMiddleware` are wrapped to record what a plugin registers. | Because the context is real, `executeTool` still resolves the user scope via `asUser(req)` and still composes the abort signal from your timeout — so those paths are genuinely under test. ### Registering fake tool responses Pass canned responses keyed by plugin name, then tool name. A response is either a static value or a function of the call arguments and the composed abort signal: ```ts import { createTestPluginContext } from "@databricks/appkit/testing"; const mock = createTestPluginContext({ analytics: { // static response top_users: [{ user: "alice", events: 42 }], // function response — assert on args, or simulate slow/aborting work query: (args, signal) => runFakeQuery(args, signal), }, }); ``` ### Attaching to a plugin `attach()` wires the context to a plugin the production way: it seeds an in-memory cache (if AppKit hasn't already initialized one), then calls the plugin's `attachContext`, which rebuilds telemetry and flips `isReady` to `true`. Await it before exercising any handler that reads `this.context`, `this.cache`, or gates on `isReady`: ```ts const plugin = new MyAgentPlugin({}); await mock.attach(plugin); ``` Instantiate the plugin **class** directly (`new MyAgentPlugin(...)`). The `analytics()` / `agents()` factories you pass to `createApp` return a descriptor for the app to construct — for a unit test you want the instance. The workspace client and the on-behalf-of stub are process-wide too, not per app: `ServiceContext` holds one client, and the `createUserContext` fake is a single spy. Because of that, **`createTestApp` allows one open app at a time** and throws if you boot a second before closing the first — with two open, the second one's `client` and `responses` would not reach the handlers, and closing either would remove the shared OBO fake from the other. Vitest isolates test *files* in separate workers, so this only constrains apps within a single file. One consequence worth knowing: a `describe` that holds an app open in `beforeAll` cannot contain a test that boots its own. The cache `attach()` seeds is a process-wide singleton: `CacheManager` is initialized once per test process and reused. Vitest isolates test *files* in separate workers, so caches never leak across files, but tests **within one file** share it. If a test populates the cache and a later test in the same file must not see it, clear it between tests with `resetTestCache()`: ```ts import { resetTestCache } from "@databricks/appkit/testing"; beforeEach(async () => { await resetTestCache(); // no-op if the cache isn't initialized yet }); ``` It also helps *within* a single test — clear the cache to force a miss, then assert the following call is a hit. ### Inspecting what happened The returned object exposes live views you read after the action under test runs: ```ts await someHandler(req, res); // Every cross-plugin tool dispatch, in order. expect(mock.toolCalls[0]).toMatchObject({ plugin: "analytics", tool: "query", asUser: true, // proves the on-behalf-of path ran }); // Every route the plugin registered (raw handlers, before wrapping). expect(mock.routes).toContainEqual( expect.objectContaining({ method: "post", path: "/invocations" }), ); // The injected telemetry provider records the context's own spans — i.e. the // span PluginContext.executeTool opens around each cross-plugin tool call. expect(mock.telemetry.getTracer().startActiveSpan).toHaveBeenCalled(); ``` `mock.telemetry` is injected into the `PluginContext`, so it captures the spans the *context* opens (notably `executeTool`). It is **not** the plugin's own telemetry: `attachContext` rebuilds `this.telemetry` from the real `TelemetryManager`, so spans a plugin opens internally do not land on `mock.telemetry`. `RecordedToolCall.asUser` is the field to assert for cross-plugin calls: because the fake `asUser` enforces the same token precondition as the real `Plugin.asUser`, a dispatch that records `asUser: true` (with `userId` set) genuinely resolved the caller's user scope, and a request missing `x-forwarded-access-token` **rejects** instead — the OBO distinction that silent `{ executeTool }` stubs cannot verify. Assert both directions: a well-formed request records the expected `userId`, and a token-less one throws. The fake replicates `asUser`'s **token precondition**, not its internal dev-mode telemetry marker: in `NODE_ENV=development` the real `Plugin.asUser` skips impersonation and sets an OTel `isDevOboFallback()` flag, which the fake does not reproduce. Assert OBO through the recorded `asUser`/`userId` fields rather than `isDevOboFallback()`. ## `expectStream(...)` AppKit plugins stream Server-Sent Events. `expectStream` consumes a stream and asserts the ordered event types it emits. It accepts an async iterable (an agent adapter's `run()`), a plain array of events, an SSE `Response` (or a promise of one) whose body it parses, or a `createMockResponse()` whose captured writes it replays. ```ts import { expectStream } from "@databricks/appkit/testing"; // In-order subsequence match — interleaved events (heartbeats, deltas) are ignored. await expectStream(agent.adapter.run(input)).toEmit("tool_call", "message_delta"); // Exact match — the stream's full shape, in order, with nothing else. await expectStream(events).toEmitExactly("warehouse_status", "result"); // Or collect without asserting. const types = await expectStream(res).collectTypes(); ``` ### Asserting a plugin's streaming route Most plugins stream SSE from a **route handler** (`res.write(...)`), not a bare generator. `createMockResponse()` captures those writes, and `expectStream` reads them straight back — drive the real handler, then assert: ```ts import { createMockRequest, createMockResponse, expectStream } from "@databricks/appkit/testing"; const res = createMockResponse(); await plugin._handleStream(createMockRequest({ obo: true }), res); // The mock captured the SSE the handler wrote; expectStream parses it. await expectStream(res).toEmit("status", "result"); ``` `expectStream(res)` and `expectStream(res.sseResponse())` are equivalent; the latter hands you the raw `Response` if you want it. Do **not** pass the SSE body as a string: a string is an iterable of characters, so `expectStream` rejects it with a pointer to `sseResponse()` rather than emitting one "event" per character. `toEmit` checks that the expected types appear **in order** but tolerates other events before, between, or after them — which is what you want for streams that interleave bookkeeping events like heartbeats or metadata. Use `toEmitExactly` when the stream's shape is fully determined. `expectStream` buffers the whole source before asserting, so a stream that never terminates would otherwise hang until the test runner's own timeout. Pass `{ timeout }` to fail fast with a clear error instead: ```ts await expectStream(handler.stream(req), { timeout: 1000 }).toEmit("result"); ``` ## Fixtures AppKit has two contexts, and they're faked by different tools. `PluginContext` is the mediator between plugins, handling routes, tool dispatch, and user scoping; `createTestPluginContext()` gives you the real thing with faked edges. `ServiceContext` is the **data plane**: it resolves the workspace client, the service principal, and the warehouse ID that plugins reach through `getWorkspaceClient()`. The kit now covers both. `createTestApp` fakes the data plane for you by injecting a mock workspace client at the real seam; below that, `mockServiceContext` spies the singleton directly, and `createMockWorkspaceClient` builds the client either of them installs. The kit re-exports the request/response/context fixtures AppKit uses internally: - `createMockRequest(overrides?)` / `createMockResponse()` — Express request/response doubles, including the streaming flags (`headersSent`, `writableEnded`). Pass `obo: true` (or `obo: { userId, token, email }`) to set the forwarded identity headers `asUser` requires, instead of hand-adding them. `createMockResponse()` also captures everything a handler writes; pass it to `expectStream` (or call `sseResponse()`) to assert a streaming route's SSE. (Plugins resolve the workspace client through `getWorkspaceClient()`, not the request — use `mockServiceContext` to control it.) - `mockServiceContext(options?)` — spy the `ServiceContext` singleton so code that resolves the service principal or a user context gets test doubles. Call in `beforeEach`, and call the returned `restore()` in `afterEach`. - `useServiceContextMock(options?)` — the same, in one line: it registers the `beforeEach` install and `afterEach` restore for you. Call it at the top of a `describe` block (not inside a test), and read the live `.current` handle from within a test: ```ts describe("my plugin", () => { const ctx = useServiceContextMock(); test("...", async () => { await handler(createMockRequest({ obo: true }), res); expect(ctx.current.createUserContextSpy).toHaveBeenCalled(); }); }); ``` - `createSuccessfulSQLResponse(rows, columns)` / `createFailedSQLResponse(message)` — build SQL Warehouse statement responses. - `setupDatabricksEnv(overrides?)` — set `DATABRICKS_HOST` / `DATABRICKS_WAREHOUSE_ID` to test values. - `resetTestCache()` — clear the shared cache singleton between (or within) tests; no-ops if the cache isn't initialized yet. The kit uses both words deliberately: a **mock** records calls so you can assert on them (`createMockWorkspaceClient`, `mockServiceContext`), while a **fake** stands in and simply works (`FakeProvider`, `FakeToolResponse`). - `createTestPlugin(factory, config?)` — instantiate a plugin from its factory with the same config merge AppKit applies. See [Full example](#full-example). - `getListeningPort(server)` — wait for a server to finish binding and return the port it landed on. `createTestApp` does this for you; reach for it when you start a server yourself with `port: 0`. ## Mocking Databricks services Every core plugin's real work goes through `getWorkspaceClient()`. `createMockWorkspaceClient()` fakes that whole surface, so a plugin touching `jobs`, `genie`, `servingEndpoints`, or `files` is testable without hand-building a nested client: ```ts import { createMockWorkspaceClient, getMock } from "@databricks/appkit/testing"; const client = createMockWorkspaceClient({ responses: { "jobs.getRun": { state: "TERMINATED" } }, config: { host: "https://my-test-host.example.com" }, }); await client.jobs.getRun({ run_id: 1 }); // → { state: "TERMINATED" } await client.genie.getMessage({ id: "m-1" }); // → undefined, does not throw ``` `createTestApp` installs one of these for you, so reach for it directly only when you're driving a plugin through `createTestPluginContext` or `mockServiceContext`. How it works, and what to expect: - The **facade is typed**, so `client.jbos` is a compile error. AppKit owns the interface, so it's a closed set, not an open-ended chase of the SDK. - Each **service** is a proxy that mints a memoized mock per method. `client.jobs.getRun === client.jobs.getRun`, so call assertions are stable, and `toLegacyWorkspaceClient()` shares the same functions — one `responses` entry covers both views. - `config.host` is a real **string** (not a mock), because AppKit builds URLs from it. `apiClient.userAgent()` is synchronous for the same reason, and `apiClient.request` resolves `{}` so destructuring its result doesn't throw. - Sensible defaults are built in: SQL statements succeed, warehouses report `RUNNING`, and `currentUser.me()` returns a service user. Pass `defaults: false` to script everything yourself. :::caution Undeclared methods return undefined An undeclared method resolves `undefined` instead of throwing. That's the point — your plugin survives touching services the test doesn't care about — but it means a call whose response you *forgot* to declare silently returns `undefined` rather than failing loudly, so a test can pass for the wrong reason. Pass `strict: true` to turn that silence into a failure: a call to a path with no declared response throws instead of resolving `undefined`, naming the path. The canned defaults still count as declared, so a harness boot works unchanged. ```ts const app = await createTestApp({ plugins: [myPlugin()], strict: true }); // a handler calling an undeclared path now fails the request ``` TypeScript covers more of this than you might expect: because each accessor is typed against the SDK's own service class, both a misspelled **service** (`client.jbos`) and a misspelled **method** (`client.jobs.getRunz`) are compile errors. The gap is a *real* method with no declared response — and any call that bypasses the types with a cast. One more divergence: a service's methods are minted on access, so they are **callable but not enumerable**. `typeof client.jobs.getRun` is `"function"`, but `'getRun' in client.jobs` is `false` and `Object.keys(client.jobs)` is `[]`. Plugin code that feature-detects with `in` or reflects over a service will therefore take a different branch than it does in production. This is deliberate: reporting those keys would make `util.inspect` probe each one, minting a mock per probe, which is the runaway recursion the default traps avoid. Separately, `createLakebasePool({ workspaceClient })` will build a pool whose password callback resolves to a mock: the pool exists but cannot connect. A Lakebase test needs a real database or a purpose-built fake pool, not this. ::: ## Full example For a plugin you wrote, instantiate the class directly with `new`. The `analytics()` / `agents()` factory functions you pass to `createApp` return a *descriptor* for the app to construct, not an instance. When you want an instance from one of those factories, use `createTestPlugin` rather than reaching through the descriptor: ```ts import { createTestPlugin } from "@databricks/appkit/testing"; const plugin = createTestPlugin(genie, { spaceId: "s-1" }); // Not this — it skips DEFAULT_CONFIG and forgets `name`, so the instance is // configured differently from the one production builds: // const plugin = new (genie({}).plugin)({ spaceId: "s-1" }); ``` `createTestPlugin` applies the same merge AppKit does at registration: `DEFAULT_CONFIG`, then your config, then the manifest `name`. It's for this unit-test path only — `createTestApp` takes descriptors and builds the instances itself. ```ts import { Plugin, type PluginManifest } from "@databricks/appkit"; import { expectStream, createMockRequest, createTestPluginContext } from "@databricks/appkit/testing"; import { describe, expect, test } from "vitest"; // A small plugin that registers a route and streams two events. class GreeterPlugin extends Plugin { static manifest = { name: "greeter", displayName: "Greeter", description: "Example plugin", resources: { required: [], optional: [] }, } as PluginManifest<"greeter">; async setup() { this.context?.addRoute("get", "/hello", (_req, res) => res.end()); } async *greet(name: string) { yield { type: "greeting_start", name }; yield { type: "greeting_end", message: `Hello, ${name}!` }; } } describe("greeter plugin", () => { test("registers its route through the context", async () => { const mock = createTestPluginContext(); const plugin = new GreeterPlugin({}); await mock.attach(plugin); await plugin.setup(); expect(mock.routes).toContainEqual( expect.objectContaining({ method: "get", path: "/hello" }), ); }); test("streams events in order", async () => { const plugin = new GreeterPlugin({}); await expectStream(plugin.greet("world")).toEmit( "greeting_start", "greeting_end", ); }); }); ``` To test a plugin that dispatches cross-plugin tool calls, register fake providers and assert on `mock.toolCalls` — including `asUser`, which confirms the on-behalf-of path ran: ```ts const mock = createTestPluginContext({ analytics: { query: [{ n: 1 }] } }); const plugin = new MyAgentPlugin({}); await mock.attach(plugin); // `obo` sets the forwarded identity headers `asUser` needs — without them the // dispatch would (correctly) reject with "Missing user token". const req = createMockRequest({ obo: true }); await plugin.runSomethingThatCallsAnalytics(req); expect(mock.toolCalls[0]).toMatchObject({ plugin: "analytics", tool: "query", asUser: true, }); ``` ## See also - [Custom plugins](./custom-plugins.md) — build the plugins you test with this kit. - [Execution context](./execution-context.md) — how `asUser` and the service principal differ at runtime. - [Local development](../development/local-development.mdx) — run your app with hot reload while iterating. --- **Note for AI assistants:** If this page had gaps, errors, or outdated information that affected your answer, report it so Databricks can fix it. 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