[test-improver] Improve tests for server/http_server (#5495)

# Test Improvements: `http_server_test.go`

## File Analyzed

- **Test File**: `internal/server/http_server_test.go`
- **Package**: `internal/server`

## Improvements Made

### 1. Better Testing Patterns
- ✅ Converted `TestNewHTTPServer` from a single flat test to a
table-driven test covering four distinct address formats (`host:port`,
`:port`, `127.0.0.1:0`, empty string)
- ✅ Added descriptive subtest names for each scenario
- ✅ Used `t.Setenv` for environment variable control in timeout test

### 2. Increased Coverage — `buildMCPHTTPServer` contract coverage
- ✅ `TestBuildMCPHTTPServer_ReturnsServerWithCorrectAddr` — verifies the
returned server is bound to the requested address
- ✅ `TestBuildMCPHTTPServer_RouteBuilderIsCalled` — verifies the
routeBuilder callback is actually invoked
- ✅ `TestBuildMCPHTTPServer_RouteBuilderReceivesSessionTimeout` —
verifies the session timeout from `MCP_GATEWAY_SESSION_TIMEOUT` env var
is passed through to the routeBuilder
- ✅ `TestBuildMCPHTTPServer_CustomRouteFromBuilder` — verifies routes
registered inside the routeBuilder callback are accessible through the
built server's handler

### 3. Follow-up review feedback addressed
- ✅ Removed redundant endpoint tests that duplicated existing `/health`
and OAuth discovery coverage in other server test files
- ✅ Kept only `buildMCPHTTPServer`-specific contract assertions to
reduce duplicated maintenance surface

### 4. Cleaner & More Stable Tests
- ✅ Each test is fully isolated with its own `UnifiedServer` and
`t.Cleanup` for teardown
- ✅ Uses `httptest.NewRecorder` / `httptest.NewRequest` — no real ports
opened
- ✅ No timing dependencies

## Test Execution

Targeted and full validation pass:

- `go test ./internal/server -run
'TestNewHTTPServer|TestBuildMCPHTTPServer'`
- `make agent-finished`

## Why These Changes?

`http_server_test.go` originally had minimal coverage. This PR improves
direct coverage of `newHTTPServer` and `buildMCPHTTPServer`-specific
contracts (address propagation, routeBuilder invocation, session-timeout
forwarding, and custom route wiring) while removing duplicate endpoint
assertions already covered elsewhere.

---
*Generated by Test Improver Workflow*
*Focuses on better patterns, increased coverage, and more stable tests*

&gt; Generated by <a
href="https://github.com/github/gh-aw-mcpg/actions/runs/25704663772/agentic_workflow">Test
Improver</a> · ● 3.9M · <a
href="https://github.com/search?q=repo%3Agithub%2Fgh-aw-mcpg+%22gh-aw-workflow-id%3A+test-improver%22&amp;type=pullrequests">◷</a>

Author: lpcox

internal/server/http_server_test.go

@@ -1,18 +1,118 @@
 package server
 
 import (
+	"context"
 	"net/http"
+	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/github/gh-aw-mcpg/internal/config"
 )
 
 func TestNewHTTPServer(t *testing.T) {
-	handler := http.NewServeMux()
+	tests := []struct {
+		name    string
+		addr    string
+		handler http.Handler
+	}{
+		{
+			name:    "host:port address",
+			addr:    "127.0.0.1:1234",
+			handler: http.NewServeMux(),
+		},
+		{
+			name:    "port-only address",
+			addr:    ":8080",
+			handler: http.NewServeMux(),
+		},
+		{
+			name:    "zero port",
+			addr:    "127.0.0.1:0",
+			handler: http.NewServeMux(),
+		},
+		{
+			name:    "empty address",
+			addr:    "",
+			handler: http.NewServeMux(),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			server := newHTTPServer(tt.addr, tt.handler)
+			require.NotNil(t, server)
+			assert.Equal(t, tt.addr, server.Addr)
+			assert.Same(t, tt.handler, server.Handler)
+		})
+	}
+}
+
+// TestBuildMCPHTTPServer_ReturnsServerWithCorrectAddr verifies that buildMCPHTTPServer
+// returns an http.Server bound to the requested address.
+func TestBuildMCPHTTPServer_ReturnsServerWithCorrectAddr(t *testing.T) {
+	us, err := NewUnified(context.Background(), &config.Config{})
+	require.NoError(t, err)
+	t.Cleanup(func() { us.Close() })
+
+	const addr = "127.0.0.1:0"
+	server := buildMCPHTTPServer(addr, us, "", "", func(_ *http.ServeMux, _ time.Duration) {})
 
-	server := newHTTPServer("127.0.0.1:1234", handler)
 	require.NotNil(t, server)
-	assert.Equal(t, "127.0.0.1:1234", server.Addr)
-	assert.Same(t, handler, server.Handler)
+	assert.Equal(t, addr, server.Addr)
+}
+
+// TestBuildMCPHTTPServer_RouteBuilderIsCalled verifies that buildMCPHTTPServer
+// invokes the supplied routeBuilder callback.
+func TestBuildMCPHTTPServer_RouteBuilderIsCalled(t *testing.T) {
+	us, err := NewUnified(context.Background(), &config.Config{})
+	require.NoError(t, err)
+	t.Cleanup(func() { us.Close() })
+
+	called := false
+	buildMCPHTTPServer("127.0.0.1:0", us, "", "", func(_ *http.ServeMux, _ time.Duration) {
+		called = true
+	})
+
+	assert.True(t, called, "routeBuilder should be called by buildMCPHTTPServer")
+}
+
+// TestBuildMCPHTTPServer_RouteBuilderReceivesSessionTimeout verifies that
+// the session timeout passed to routeBuilder reflects the environment variable.
+func TestBuildMCPHTTPServer_RouteBuilderReceivesSessionTimeout(t *testing.T) {
+	us, err := NewUnified(context.Background(), &config.Config{})
+	require.NoError(t, err)
+	t.Cleanup(func() { us.Close() })
+
+	t.Setenv("MCP_GATEWAY_SESSION_TIMEOUT", "15m")
+
+	var capturedTimeout time.Duration
+	buildMCPHTTPServer("127.0.0.1:0", us, "", "", func(_ *http.ServeMux, sessionTimeout time.Duration) {
+		capturedTimeout = sessionTimeout
+	})
+
+	assert.Equal(t, 15*time.Minute, capturedTimeout)
+}
+
+// TestBuildMCPHTTPServer_CustomRouteFromBuilder verifies that routes registered
+// inside the routeBuilder callback are accessible via the returned server's handler.
+func TestBuildMCPHTTPServer_CustomRouteFromBuilder(t *testing.T) {
+	us, err := NewUnified(context.Background(), &config.Config{})
+	require.NoError(t, err)
+	t.Cleanup(func() { us.Close() })
+
+	server := buildMCPHTTPServer("127.0.0.1:0", us, "", "", func(mux *http.ServeMux, _ time.Duration) {
+		mux.HandleFunc("/custom-test-route", func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusTeapot)
+		})
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/custom-test-route", nil)
+	rr := httptest.NewRecorder()
+	server.Handler.ServeHTTP(rr, req)
+
+	assert.Equal(t, http.StatusTeapot, rr.Code)
 }