Rewrite tests to run without a database

- Unit tests use an in-memory fake database (internal/testutil/fakedb),
  temp folders and httptest; `go test ./...` needs no Docker or env vars
- Integration tests (build tag "integration") start PostgreSQL with
  testcontainers: migrations step by step, SQL dumps (skipped if
  missing) and a full sync against a real database
- Removed tests that only checked copies of the logic or had empty
  bodies, the broken root integration_test.go, compose.test.yaml and
  .env.test with hardcoded paths
- testMusic MP3s replaced with tiny placeholders (sync never decodes
  audio), 194 MB -> 168 KB

cmd/web/search_test.go

@@ -0,0 +1,100 @@
+package web
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"music-server/internal/backend"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var soundtracks = []string{
+	"Call of Duty: Modern Warfare",
+	"Final Fantasy VII",
+	"Joe & Mac",
+	"Kingdom Hearts",
+	"Lemmings (SNES + Mega Drive)",
+	"MG",
+	"Metal Gear Solid 4 - Guns of the Patriots",
+	"Pokémon HeartGold & SoulSilver",
+	"Resident Evil 2 (Remake)",
+	"Ys III - Wanderers from Ys (+The Oath in Felghana)",
+}
+
+func newCache(names []string) *backend.SearchCache {
+	return backend.NewSearchCache(func(context.Context) ([]string, error) { return names, nil })
+}
+
+func searchData(t *testing.T) []backend.SoundtrackData {
+	data, err := newCache(soundtracks).Get(context.Background())
+	require.NoError(t, err)
+	return data
+}
+
+func TestSearch(t *testing.T) {
+	data := searchData(t)
+	tests := []struct {
+		query string
+		want  []string
+	}{
+		// Exact (case-insensitive) substring
+		{"resident", []string{"Resident Evil 2 (Remake)"}},
+		// Ignoring spaces and special characters
+		{"joeandmac", []string{"Joe & Mac"}},
+		{"snes+mega", []string{"Lemmings (SNES + Mega Drive)"}},
+		{"pokemon", []string{"Pokémon HeartGold & SoulSilver"}},
+		// Letters in order
+		{"codmw", []string{"Call of Duty: Modern Warfare"}},
+		{"mgs4gotp", []string{"Metal Gear Solid 4 - Guns of the Patriots"}},
+		{"re2r", []string{"Resident Evil 2 (Remake)"}},
+		// No match
+		{"zzz", nil},
+		// Regex special characters are plain text
+		{"(remake)", []string{"Resident Evil 2 (Remake)"}},
+		{"[", nil},
+	}
+	for _, tt := range tests {
+		t.Run(tt.query, func(t *testing.T) {
+			assert.Equal(t, tt.want, search(tt.query, data))
+		})
+	}
+}
+
+func TestSearchEmptyReturnsEverything(t *testing.T) {
+	assert.Equal(t, soundtracks, search("", searchData(t)))
+}
+
+func TestSearchOrdering(t *testing.T) {
+	// "MG" is an exact match, "Metal Gear Solid..." only matches by letters in order.
+	results := search("mg", searchData(t))
+	require.GreaterOrEqual(t, len(results), 2)
+	assert.Equal(t, "MG", results[0])
+	assert.Contains(t, results, "Metal Gear Solid 4 - Guns of the Patriots")
+}
+
+func TestSearchHandler(t *testing.T) {
+	handler := NewSearchHandler(newCache(soundtracks))
+	req := httptest.NewRequest(http.MethodPost, "/find", strings.NewReader(url.Values{"search_term": {"kingdom"}}.Encode()))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Contains(t, rec.Body.String(), "Kingdom Hearts")
+	assert.NotContains(t, rec.Body.String(), "Final Fantasy")
+}
+
+func TestSearchHandlerLoadError(t *testing.T) {
+	cache := backend.NewSearchCache(func(context.Context) ([]string, error) { return nil, errors.New("db down") })
+	rec := httptest.NewRecorder()
+	NewSearchHandler(cache).ServeHTTP(rec, httptest.NewRequest(http.MethodPost, "/find", nil))
+	assert.Equal(t, http.StatusInternalServerError, rec.Code)
+}