test(coverage): twin StorageExceeded arm + ResourceLogs/streamLogsSSE error arms

Cover the seam2-reachable arms in internal/handlers:
- ProvisionForTwin StorageExceeded warning arm (db.go:574 / cache.go:502 /
  nosql.go:507) via the checkStorageQuota seam forced to exceeded=true, driven
  through the bufconn fakeProvisioner twin pipeline to a real 201.
- ResourceLogs error/edge arms (logs.go): lookup_failed (closed DB),
  tail<1 clamp, pods_unavailable (List reactor error).
- streamLogsSSE WriteString-error arms (sse_logs.go:61 + 72) via a size-1
  bufio buffer over an always-failing writer.

No production behaviour change; all new lines covered by new tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mastermanas805

internal/handlers/logs_resourcelogs_twinlogs_test.go

@@ -0,0 +1,98 @@
+package handlers_test
+
+// logs_resourcelogs_twinlogs_test.go — covers the error/edge arms of
+// LogsHandler.ResourceLogs (logs.go) that logs_coverage_test.go leaves open:
+//
+//	logs.go:157-158  — lookup_failed: GetResourceByToken returns a non-NotFound
+//	                   error (driven with a closed DB).
+//	logs.go:194-196  — tail clamp: ?tail=0 (n<1) clamps up to 1.
+//	logs.go:206-211  — pods_unavailable: the pod List call returns an error
+//	                   (driven with a PrependReactor on the fake clientset).
+//
+// The clientset is the in-memory k8s fake (SetClientset seam), so these run
+// under CI's postgres-only matrix without a live cluster.
+
+import (
+	"errors"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	k8sfake "k8s.io/client-go/kubernetes/fake"
+	k8stesting "k8s.io/client-go/testing"
+
+	"instant.dev/internal/handlers"
+	"instant.dev/internal/testhelpers"
+)
+
+// TestLogs_LookupFailed_503 drives logs.go:157-158: a DB error (not a
+// not-found) on GetResourceByToken returns 503 lookup_failed. We build the
+// handler against a CLOSED *sql.DB so the query fails with a driver error that
+// is NOT *models.ErrResourceNotFound.
+func TestLogs_LookupFailed_503(t *testing.T) {
+	db, _ := testhelpers.SetupTestDB(t)
+	h := handlers.NewLogsHandler(db)
+	h.SetClientset(k8sfake.NewSimpleClientset())
+	// Close the DB now so GetResourceByToken's query returns a driver error
+	// (sql.ErrConnDone) — NOT a *models.ErrResourceNotFound — driving the
+	// lookup_failed 503 arm rather than the not_found 404 arm.
+	require.NoError(t, db.Close())
+
+	app := logsTestApp(t, db, h)
+	// A syntactically valid UUID so we pass the parse gate and reach the lookup.
+	resp := logsGet(t, app, "11111111-1111-1111-1111-111111111111", "")
+	defer resp.Body.Close()
+	assert.Equal(t, http.StatusServiceUnavailable, resp.StatusCode)
+}
+
+// TestLogs_TailClampLow_StreamsSSE drives logs.go:194-196: ?tail=0 (n<1) clamps
+// up to 1 and the happy path still streams. Needs a pod in the fake clientset.
+func TestLogs_TailClampLow_StreamsSSE(t *testing.T) {
+	db, clean := testhelpers.SetupTestDB(t)
+	defer clean()
+
+	const ns = "ns-clamp-low"
+	cs := k8sfake.NewSimpleClientset(&corev1.Pod{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "postgres-0",
+			Namespace: ns,
+			Labels:    map[string]string{"app": "postgres"},
+		},
+	})
+	h := handlers.NewLogsHandler(db)
+	h.SetClientset(cs)
+	app := logsTestApp(t, db, h)
+
+	token := seedLogsResource(t, db, "postgres", "growth", "active", ns)
+	resp := logsGet(t, app, token, "tail=0") // n<1 → clamp to 1
+	defer resp.Body.Close()
+	require.Equal(t, http.StatusOK, resp.StatusCode)
+	assert.Equal(t, "text/event-stream", resp.Header.Get("Content-Type"))
+}
+
+// TestLogs_ListPodsError_503 drives logs.go:206-211: the pod List call errors.
+// A PrependReactor on the fake clientset makes List("pods") return an error so
+// the pods_unavailable arm runs (distinct from the empty-list pod_not_found arm
+// already covered).
+func TestLogs_ListPodsError_503(t *testing.T) {
+	db, clean := testhelpers.SetupTestDB(t)
+	defer clean()
+
+	cs := k8sfake.NewSimpleClientset()
+	cs.PrependReactor("list", "pods",
+		func(action k8stesting.Action) (handled bool, ret runtime.Object, err error) {
+			return true, nil, errors.New("apiserver unreachable")
+		})
+	h := handlers.NewLogsHandler(db)
+	h.SetClientset(cs)
+	app := logsTestApp(t, db, h)
+
+	token := seedLogsResource(t, db, "postgres", "growth", "active", "ns-list-err")
+	resp := logsGet(t, app, token, "")
+	defer resp.Body.Close()
+	assert.Equal(t, http.StatusServiceUnavailable, resp.StatusCode)
+}

internal/handlers/sse_logs_writeerr_twinlogs_test.go

@@ -0,0 +1,85 @@
+package handlers
+
+// sse_logs_writeerr_twinlogs_test.go — covers the two write-error early-return
+// arms of streamLogsSSE (sse_logs.go) that the existing sse_logs_test.go leaves
+// open because its failingWriter only ever surfaces the error at the *Flush*
+// call (line 64), never at the WriteString call itself:
+//
+//	sse_logs.go:61-63  — WriteString of a data line returns an error → return.
+//	sse_logs.go:72-74  — WriteString of the end marker returns an error → return.
+//
+// A bufio.Writer's WriteString only returns an error when an internal flush
+// (forced when its buffer fills) hits the underlying writer's error. The
+// existing tests use the default 4 KiB buffer, so the small SSE lines never
+// force a mid-WriteString flush — the error always lands on the explicit
+// w.Flush() instead. Wrapping an immediately-failing writer in a size-1 bufio
+// buffer forces the flush to happen *inside* WriteString, surfacing the error
+// at lines 61 and 72.
+
+import (
+	"bufio"
+	"strings"
+	"testing"
+)
+
+// alwaysFailWriter fails on the very first Write — modelling a fasthttp client
+// that disconnected before any byte landed.
+type alwaysFailWriter struct{ writes int }
+
+func (a *alwaysFailWriter) Write(p []byte) (int, error) {
+	a.writes++
+	return 0, errWriteClosed
+}
+
+// errWriteClosed is a sentinel write error (kept as a package-level var so the
+// closure above stays allocation-free and the intent is named).
+var errWriteClosed = &writeClosedError{}
+
+type writeClosedError struct{}
+
+func (*writeClosedError) Error() string { return "writer closed" }
+
+// TestStreamLogsSSE_DataWriteStringError_BreaksPump drives sse_logs.go:61-63:
+// the WriteString of a data line returns an error (not just the later Flush),
+// so the pump returns immediately and the deferred Close + cancel still run.
+func TestStreamLogsSSE_DataWriteStringError_BreaksPump(t *testing.T) {
+	stream := &trackedStream{Reader: strings.NewReader("a line that exceeds one byte\nsecond line\n")}
+	// size-1 buffer → the first WriteString forces an internal flush mid-write,
+	// surfacing the underlying writer error from WriteString itself (line 61),
+	// not from the explicit Flush (line 64).
+	fw := &alwaysFailWriter{}
+	w := bufio.NewWriterSize(fw, 1)
+
+	cancelled := false
+	streamLogsSSE(w, stream, func() { cancelled = true })
+
+	if stream.closes != 1 {
+		t.Errorf("stream Close called %d times after WriteString error, want 1", stream.closes)
+	}
+	if !cancelled {
+		t.Error("cancel not invoked after data-line WriteString error")
+	}
+}
+
+// TestStreamLogsSSE_EndMarkerWriteStringError drives sse_logs.go:72-74: an empty
+// stream writes no data lines, then the end-marker WriteString hits the failing
+// underlying writer (via the size-1 buffer flush) and returns — exercising the
+// end-marker write-error branch. Teardown (Close + cancel) still runs via defer.
+func TestStreamLogsSSE_EndMarkerWriteStringError(t *testing.T) {
+	stream := &trackedStream{Reader: strings.NewReader("")} // no data lines
+	fw := &alwaysFailWriter{}
+	w := bufio.NewWriterSize(fw, 1)
+
+	cancelled := false
+	streamLogsSSE(w, stream, func() { cancelled = true })
+
+	if fw.writes == 0 {
+		t.Error("end-marker WriteString did not reach the underlying writer")
+	}
+	if stream.closes != 1 {
+		t.Errorf("stream Close called %d times after end-marker write error, want 1", stream.closes)
+	}
+	if !cancelled {
+		t.Error("cancel not invoked after end-marker WriteString error")
+	}
+}

internal/handlers/twin_storage_exceeded_twinlogs_test.go

@@ -0,0 +1,112 @@
+package handlers_test
+
+// twin_storage_exceeded_twinlogs_test.go — covers the `if res.StorageExceeded`
+// warning arm of the three twin renderers:
+//
+//	db.go:574    DBHandler.ProvisionForTwin
+//	cache.go:502 CacheHandler.ProvisionForTwin
+//	nosql.go:507 NoSQLHandler.ProvisionForTwin
+//
+// That arm sets resp["warning"] + the X-Instant-Notice header, and is reachable
+// only when ProvisionForTwinCore returns StorageExceeded=true — a state that
+// requires a freshly-twinned resource to already exceed its tier's storage cap.
+// The checkStorageQuota seam (seams.go, driven by forceStorageExceeded in
+// storage_exceeded_seam2_test.go) forces exceeded=true at exactly the Core gate,
+// so the renderer takes the warning arm and surfaces it on the 201 response.
+//
+// Backend is the bufconn-backed fakeProvisioner from
+// coverage_provisioner_grpc_test.go (setupGRPCProvFixture), so the twin pipeline
+// reaches a real 201 (not a 503) under CI's postgres-only matrix — unlike the
+// live-backend seam2 anon/auth tests which skip when the customer backend is
+// unreachable.
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"instant.dev/internal/testhelpers"
+)
+
+// postTwinDevRaw POSTs a single twin to the development env (which bypasses the
+// approval gate) and returns the raw response plus the decoded warning field, so
+// a test can assert both the X-Instant-Notice header and the warning JSON the
+// StorageExceeded arm sets.
+func postTwinDevRaw(t *testing.T, fx grpcProvFixture, sourceToken, jwt string) (*http.Response, string) {
+	t.Helper()
+	b, _ := json.Marshal(map[string]any{"env": "development"})
+	req := httptest.NewRequest(http.MethodPost,
+		"/api/v1/resources/"+sourceToken+"/provision-twin", strings.NewReader(string(b)))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+jwt)
+	resp, err := fx.app.Test(req, 15000)
+	require.NoError(t, err)
+	raw, _ := io.ReadAll(resp.Body)
+	var parsed map[string]any
+	_ = json.Unmarshal(raw, &parsed)
+	warning, _ := parsed["warning"].(string)
+	return resp, warning
+}
+
+// assertTwinWarningArm asserts the twin renderer surfaced the storage-limit
+// warning that the StorageExceeded arm sets (both the JSON field and the notice
+// header).
+func assertTwinWarningArm(t *testing.T, resp *http.Response, warning string) {
+	t.Helper()
+	require.Equal(t, http.StatusCreated, resp.StatusCode)
+	assert.Equal(t, "storage_limit_reached", resp.Header.Get("X-Instant-Notice"),
+		"StorageExceeded twin arm must stamp the X-Instant-Notice header")
+	assert.Contains(t, warning, "Storage limit reached",
+		"StorageExceeded twin arm must surface the warning field")
+}
+
+func TestTwin_DB_StorageExceeded_WarningArm(t *testing.T) {
+	restore := forceStorageExceeded(t)
+	defer restore()
+
+	fake := &fakeProvisioner{}
+	fx := setupGRPCProvFixture(t, fake, false)
+	teamID := testhelpers.MustCreateTeamDB(t, fx.db, "pro")
+	jwt := authSessionJWT(t, fx.db, teamID)
+	_, srcToken := seedSourceResource(t, fx.db, teamID, "postgres", "pro", "production")
+
+	resp, warning := postTwinDevRaw(t, fx, srcToken, jwt)
+	defer resp.Body.Close()
+	assertTwinWarningArm(t, resp, warning)
+}
+
+func TestTwin_Cache_StorageExceeded_WarningArm(t *testing.T) {
+	restore := forceStorageExceeded(t)
+	defer restore()
+
+	fake := &fakeProvisioner{}
+	fx := setupGRPCProvFixture(t, fake, false)
+	teamID := testhelpers.MustCreateTeamDB(t, fx.db, "pro")
+	jwt := authSessionJWT(t, fx.db, teamID)
+	_, srcToken := seedSourceResource(t, fx.db, teamID, "redis", "pro", "production")
+
+	resp, warning := postTwinDevRaw(t, fx, srcToken, jwt)
+	defer resp.Body.Close()
+	assertTwinWarningArm(t, resp, warning)
+}
+
+func TestTwin_NoSQL_StorageExceeded_WarningArm(t *testing.T) {
+	restore := forceStorageExceeded(t)
+	defer restore()
+
+	fake := &fakeProvisioner{}
+	fx := setupGRPCProvFixture(t, fake, false)
+	teamID := testhelpers.MustCreateTeamDB(t, fx.db, "pro")
+	jwt := authSessionJWT(t, fx.db, teamID)
+	_, srcToken := seedSourceResource(t, fx.db, teamID, "mongodb", "pro", "production")
+
+	resp, warning := postTwinDevRaw(t, fx, srcToken, jwt)
+	defer resp.Body.Close()
+	assertTwinWarningArm(t, resp, warning)
+}