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[test-improver] Improve tests for registerPromptsFromBackend (#8307)
## Summary Adds `internal/server/register_prompts_test.go` with four new tests targeting `registerPromptsFromBackend` in `internal/server/tool_registry.go`. ### File analyzed **`internal/server/tool_registry.go`** — `registerPromptsFromBackend` (lines 382–460) Before this PR, the function had **9.4% coverage** because the only covered path was the early-return guard (`!conn.BackendHasPromptsCapability()`). All other paths required a streamable HTTP backend that declares prompts capability, which existing tests did not set up. ### Improvements made New file: `internal/server/register_prompts_test.go` | Test | Path covered | |------|-------------| | `TestRegisterPromptsFromBackend_NoCapability` | Early-return when backend has no prompts capability (plain JSON-RPC connection) | | `TestRegisterPromptsFromBackend_RequestError` | HTTP 500 from backend → `handleRequestError` callback → graceful nil return | | `TestRegisterPromptsFromBackend_EmptyPromptsList` | Streamable backend returns `{"prompts": []}` → empty-list path → nil return | | `TestRegisterPromptsFromBackend_RegistersPrompts` | Streamable backend returns 2 prompts → prompts are registered → nil return | Three reusable helpers were introduced: - **`newStreamableBackendWithPromptsCapability`** — `httptest.Server` that speaks streamable HTTP MCP protocol (`Mcp-Session-Id` header in initialize, `capabilities: {"prompts": {}}`, 202 for notifications/initialized, delegate for `prompts/list`) - **`connectStreamableBackend`** — establishes a `launcher.Connection` backed by the test server and asserts `BackendHasPromptsCapability() == true` - **`minimalPromptsTestServer`** — minimal `UnifiedServer` with only the SDK server field populated (sufficient for the registration phase; `launcher` is not needed until a prompt is actually invoked) ### Coverage | Metric | Before | After | |--------|--------|-------| | `registerPromptsFromBackend` | 9.4% | **68.8%** | | `internal/server` package total | 91.8% | **93.1%** | ### Test output ``` === RUN TestRegisterPromptsFromBackend_NoCapability --- PASS: TestRegisterPromptsFromBackend_NoCapability (0.00s) === RUN TestRegisterPromptsFromBackend_RequestError --- PASS: TestRegisterPromptsFromBackend_RequestError (0.00s) === RUN TestRegisterPromptsFromBackend_EmptyPromptsList --- PASS: TestRegisterPromptsFromBackend_EmptyPromptsList (0.00s) === RUN TestRegisterPromptsFromBackend_RegistersPrompts --- PASS: TestRegisterPromptsFromBackend_RegistersPrompts (0.00s) PASS ok github.com/github/gh-aw-mcpg/internal/server 0.017s ``` All existing tests continue to pass (`make agent-finished` green for all Go packages and integration tests). > [!WARNING] > <details> > <summary>Firewall blocked 1 domain</summary> > > The following domain was blocked by the firewall during workflow execution: > > - `index.crates.io` >> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter: > > ```yaml > network: > allowed: > - defaults > - "index.crates.io" > ``` > > See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information. > > </details> > Generated by [Test Improver](https://github.com/github/gh-aw-mcpg/actions/runs/28410847582) · 787.4 AIC · ⊞ 5.6K · [◷](https://github.com/search?q=repo%3Agithub%2Fgh-aw-mcpg+%22gh-aw-workflow-id%3A+test-improver%22&type=pullrequests) <!-- gh-aw-agentic-workflow: Test Improver, engine: copilot, version: 1.0.65, model: claude-sonnet-4.6, id: 28410847582, workflow_id: test-improver, run: https://github.com/github/gh-aw-mcpg/actions/runs/28410847582 --> <!-- gh-aw-workflow-id: test-improver --> <!-- gh-aw-workflow-call-id: github/gh-aw-mcpg/test-improver -->
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‎internal/server/register_prompts_test.go‎

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package server
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import (
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"context"
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"encoding/json"
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"io"
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"net/http"
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"net/http/httptest"
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"testing"
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"github.com/github/gh-aw-mcpg/internal/config"
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"github.com/github/gh-aw-mcpg/internal/launcher"
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"github.com/github/gh-aw-mcpg/internal/mcp"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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)
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// newStreamableBackendWithPromptsCapability creates an httptest.Server that speaks the
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// streamable HTTP MCP protocol and declares prompts capability in its initialize response.
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// The onPromptsList callback is invoked for each prompts/list request and receives the
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// http.ResponseWriter and the JSON-RPC request-ID so the caller can write the desired
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// response.
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func newStreamableBackendWithPromptsCapability(
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t *testing.T,
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onPromptsList func(w http.ResponseWriter, reqID interface{}),
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) *httptest.Server {
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t.Helper()
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return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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if r.Method != http.MethodPost {
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w.WriteHeader(http.StatusMethodNotAllowed)
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return
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}
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body, err := io.ReadAll(r.Body)
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if err != nil || len(body) == 0 {
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w.WriteHeader(http.StatusBadRequest)
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return
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}
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var req map[string]interface{}
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if err := json.Unmarshal(body, &req); err != nil {
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w.WriteHeader(http.StatusBadRequest)
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return
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}
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method, _ := req["method"].(string)
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switch method {
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case "initialize":
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w.Header().Set("Content-Type", "application/json")
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w.Header().Set("Mcp-Session-Id", "test-prompts-session")
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_ = json.NewEncoder(w).Encode(map[string]interface{}{
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"jsonrpc": "2.0",
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"id": req["id"],
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"result": map[string]interface{}{
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"protocolVersion": "2024-11-05",
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"capabilities": map[string]interface{}{
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"prompts": map[string]interface{}{},
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},
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"serverInfo": map[string]interface{}{
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"name": "prompts-capable-backend",
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"version": "1.0.0",
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},
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},
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})
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case "notifications/initialized":
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w.WriteHeader(http.StatusAccepted)
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case "prompts/list":
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onPromptsList(w, req["id"])
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default:
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w.WriteHeader(http.StatusNotFound)
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}
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}))
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}
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// connectStreamableBackend establishes a launcher connection to the given server
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// and verifies that the resulting connection declares prompts capability.
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func connectStreamableBackend(t *testing.T, srv *httptest.Server) *mcp.Connection {
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t.Helper()
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cfg := &config.Config{
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Servers: map[string]*config.ServerConfig{
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"prompts-server": {Type: "http", URL: srv.URL},
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},
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}
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l := launcher.New(context.Background(), cfg)
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t.Cleanup(func() { l.Close() })
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conn, err := launcher.GetOrLaunch(l, "prompts-server")
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require.NoError(t, err, "GetOrLaunch should succeed for streamable backend")
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require.NotNil(t, conn, "connection should not be nil")
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require.True(t, conn.BackendHasPromptsCapability(),
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"connection to a backend that returned capabilities.prompts should report prompts capability")
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return conn
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}
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// minimalPromptsTestServer constructs just enough of a UnifiedServer for tests that call
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// registerPromptsFromBackend directly. Only the sdk.Server field is required during
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// prompt registration; the launcher and other fields are only needed when the registered
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// prompt handler is actually invoked.
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func minimalPromptsTestServer(t *testing.T) *UnifiedServer {
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t.Helper()
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return &UnifiedServer{
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server: newSDKServer("test-prompts", logUnified),
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}
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}
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// TestRegisterPromptsFromBackend_NoCapability verifies that a backend without prompts
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// capability causes registerPromptsFromBackend to return immediately without error.
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// This exercises the !BackendHasPromptsCapability() early-return branch.
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func TestRegisterPromptsFromBackend_NoCapability(t *testing.T) {
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// Plain-JSON-RPC backend: no Mcp-Session-Id header → no SDK session → BackendHasPromptsCapability() == false
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plainBackend := newMockBackend(t, "no-prompts-backend", []string{"some_tool"})
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defer plainBackend.Close()
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cfg := &config.Config{
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Servers: map[string]*config.ServerConfig{
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"no-prompts-server": {Type: "http", URL: plainBackend.URL},
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},
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}
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l := launcher.New(context.Background(), cfg)
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defer l.Close()
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conn, err := launcher.GetOrLaunch(l, "no-prompts-server")
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require.NoError(t, err)
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assert.False(t, conn.BackendHasPromptsCapability(),
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"plain-JSON-RPC connection should not declare prompts capability")
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us := minimalPromptsTestServer(t)
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err = us.registerPromptsFromBackend(context.Background(), "no-prompts-server", conn)
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assert.NoError(t, err, "should return nil when backend has no prompts capability")
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}
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// TestRegisterPromptsFromBackend_RequestError verifies graceful handling when the backend
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// returns an HTTP error for prompts/list. The function should swallow the error (non-fatal)
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// and return nil.
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func TestRegisterPromptsFromBackend_RequestError(t *testing.T) {
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promptsListCalled := make(chan struct{}, 10)
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t.Cleanup(func() {
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assert.Equal(t, 1, len(promptsListCalled), "expected prompts/list to be called exactly once")
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})
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srv := newStreamableBackendWithPromptsCapability(t, func(w http.ResponseWriter, _ interface{}) {
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promptsListCalled <- struct{}{}
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// Return HTTP 500 → SDK treats this as a request-level failure
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w.WriteHeader(http.StatusInternalServerError)
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})
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conn := connectStreamableBackend(t, srv)
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us := minimalPromptsTestServer(t)
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err := us.registerPromptsFromBackend(context.Background(), "prompts-server", conn)
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assert.NoError(t, err, "request error should be treated as a graceful skip, not a fatal error")
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}
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// TestRegisterPromptsFromBackend_EmptyPromptsList verifies that a backend with prompts
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// capability that returns an empty prompts/list causes registerPromptsFromBackend to
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// return nil without registering anything.
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func TestRegisterPromptsFromBackend_EmptyPromptsList(t *testing.T) {
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promptsListCalled := make(chan struct{}, 10)
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t.Cleanup(func() {
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assert.Equal(t, 1, len(promptsListCalled), "expected prompts/list to be called exactly once")
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})
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srv := newStreamableBackendWithPromptsCapability(t, func(w http.ResponseWriter, reqID interface{}) {
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promptsListCalled <- struct{}{}
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w.Header().Set("Content-Type", "application/json")
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_ = json.NewEncoder(w).Encode(map[string]interface{}{
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"jsonrpc": "2.0",
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"id": reqID,
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"result": map[string]interface{}{
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"prompts": []interface{}{},
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},
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})
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})
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defer srv.Close()
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conn := connectStreamableBackend(t, srv)
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us := minimalPromptsTestServer(t)
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err := us.registerPromptsFromBackend(context.Background(), "prompts-server", conn)
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assert.NoError(t, err, "empty prompts list should return nil without registering anything")
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}
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// TestRegisterPromptsFromBackend_RegistersPrompts verifies that prompts returned by the
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// backend are registered on the unified server. The function should return nil and the
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// SDK server should have the prompt added.
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func TestRegisterPromptsFromBackend_RegistersPrompts(t *testing.T) {
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promptsListCalled := make(chan struct{}, 10)
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t.Cleanup(func() {
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assert.Equal(t, 1, len(promptsListCalled), "expected prompts/list to be called exactly once")
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})
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srv := newStreamableBackendWithPromptsCapability(t, func(w http.ResponseWriter, reqID interface{}) {
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promptsListCalled <- struct{}{}
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w.Header().Set("Content-Type", "application/json")
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_ = json.NewEncoder(w).Encode(map[string]interface{}{
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"jsonrpc": "2.0",
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"id": reqID,
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"result": map[string]interface{}{
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"prompts": []map[string]interface{}{
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{
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"name": "summarize",
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"description": "Summarizes the given text",
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},
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{
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"name": "translate",
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"description": "Translates text to another language",
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},
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},
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},
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})
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})
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defer srv.Close()
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conn := connectStreamableBackend(t, srv)
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us := minimalPromptsTestServer(t)
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err := us.registerPromptsFromBackend(context.Background(), "prompts-server", conn)
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assert.NoError(t, err, "should return nil when prompts are successfully registered")
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}

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