diff --git a/internal/api/v1/scheme_test.go b/internal/api/v1/scheme_test.go
new file mode 100644
index 0000000..e74ce67
--- /dev/null
+++ b/internal/api/v1/scheme_test.go
@@ -0,0 +1,20 @@
+package v1
+
+import (
+	"crypto/tls"
+	"net/http"
+	"testing"
+)
+
+func TestScheme(t *testing.T) {
+	if got := scheme(&http.Request{TLS: &tls.ConnectionState{}}); got != "https" {
+		t.Errorf("TLS request scheme = %q, want https", got)
+	}
+	r := &http.Request{Header: http.Header{"X-Forwarded-Proto": {"https"}}}
+	if got := scheme(r); got != "https" {
+		t.Errorf("X-Forwarded-Proto scheme = %q, want https", got)
+	}
+	if got := scheme(&http.Request{Header: http.Header{}}); got != "http" {
+		t.Errorf("default scheme = %q, want http", got)
+	}
+}
diff --git a/internal/api/v2/errorpaths_test.go b/internal/api/v2/errorpaths_test.go
new file mode 100644
index 0000000..56bd343
--- /dev/null
+++ b/internal/api/v2/errorpaths_test.go
@@ -0,0 +1,123 @@
+package v2
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+)
+
+var testDSN string
+
+func TestMain(m *testing.M) {
+	ctx := context.Background()
+	dsn, terminate, err := testsupport.StartPostgres(ctx)
+	if err != nil {
+		os.Exit(m.Run())
+	}
+	testDSN = dsn
+	code := m.Run()
+	terminate()
+	if code != 0 {
+		os.Exit(code)
+	}
+}
+
+// closedDB returns a DB whose pool has been closed, so every query fails —
+// used to drive the handlers' error branches.
+func closedDB(t *testing.T) *database.DB {
+	t.Helper()
+	if testDSN == "" {
+		t.Skip("Docker unavailable")
+	}
+	db, err := database.New(testDSN)
+	if err != nil {
+		t.Fatalf("new db: %v", err)
+	}
+	db.Close()
+	return db
+}
+
+func do(t *testing.T, h http.Handler, method, path, body string) int {
+	t.Helper()
+	var r io.Reader
+	if body != "" {
+		r = strings.NewReader(body)
+	}
+	req := httptest.NewRequest(method, path, r)
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, req)
+	return w.Code
+}
+
+func TestRemotesErrorPaths(t *testing.T) {
+	h := NewRemotesHandler(closedDB(t)).Routes()
+	if c := do(t, h, "GET", "/", ""); c != 500 {
+		t.Errorf("list with dead db = %d, want 500", c)
+	}
+	if c := do(t, h, "POST", "/", `{"name":"x","package_type":"generic","repo_type":"remote","base_url":"https://x"}`); c != 500 {
+		t.Errorf("create with dead db = %d, want 500", c)
+	}
+	if c := do(t, h, "PUT", "/x", `{"package_type":"generic","base_url":"https://x"}`); c != 500 {
+		t.Errorf("update with dead db = %d, want 500", c)
+	}
+	if c := do(t, h, "GET", "/x", ""); c != 404 {
+		t.Errorf("get missing = %d, want 404", c)
+	}
+	if c := do(t, h, "DELETE", "/x", ""); c != 500 {
+		t.Errorf("delete with dead db = %d, want 500", c)
+	}
+	// Bad request bodies never reach the db.
+	if c := do(t, h, "POST", "/", `not json`); c != 400 {
+		t.Errorf("invalid json = %d, want 400", c)
+	}
+}
+
+func TestVirtualsErrorPaths(t *testing.T) {
+	h := NewVirtualsHandler(closedDB(t)).Routes()
+	if c := do(t, h, "GET", "/", ""); c != 500 {
+		t.Errorf("list = %d, want 500", c)
+	}
+	if c := do(t, h, "GET", "/x", ""); c != 404 {
+		t.Errorf("get missing = %d, want 404", c)
+	}
+	if c := do(t, h, "POST", "/", `{"name":"v","package_type":"helm","members":["a"]}`); c != 500 {
+		t.Errorf("create = %d, want 500", c)
+	}
+	if c := do(t, h, "PUT", "/v", `{"package_type":"helm","members":["a"]}`); c != 500 {
+		t.Errorf("update = %d, want 500", c)
+	}
+	if c := do(t, h, "DELETE", "/v", ""); c != 500 {
+		t.Errorf("delete = %d, want 500", c)
+	}
+}
+
+func TestStatsErrorPaths(t *testing.T) {
+	h := NewStatsHandler(closedDB(t)).Routes()
+	for _, p := range []string{"/", "/top-remotes", "/top-files-by-hits", "/top-files-by-bandwidth"} {
+		if c := do(t, h, "GET", p, ""); c != 500 {
+			t.Errorf("stats %s = %d, want 500", p, c)
+		}
+	}
+}
+
+func TestLocalErrorPaths(t *testing.T) {
+	h := NewLocalHandler(closedDB(t), nil).Routes()
+	// GetRemote fails on the closed db -> not found.
+	if c := do(t, h, "PUT", "/x/files/a.bin", "data"); c != 404 {
+		t.Errorf("upload unknown repo = %d, want 404", c)
+	}
+	// download / remove hit the db and 500.
+	if c := do(t, h, "GET", "/x/files/a.bin", ""); c != 500 {
+		t.Errorf("download = %d, want 500", c)
+	}
+	if c := do(t, h, "DELETE", "/x/files/a.bin", ""); c != 500 {
+		t.Errorf("remove = %d, want 500", c)
+	}
+}
diff --git a/internal/provider/rpm/rpm_meta_test.go b/internal/provider/rpm/rpm_meta_test.go
index 64ed91e..9a0c525 100644
--- a/internal/provider/rpm/rpm_meta_test.go
+++ b/internal/provider/rpm/rpm_meta_test.go
@@ -192,6 +192,41 @@ func TestRPMPrimaryXMLContents(t *testing.T) {
 	}
 }
 
+func TestRPMContentTypeAndHelpers(t *testing.T) {
+	p := &Provider{}
+	for path, want := range map[string]string{
+		"x.rpm":                     "application/x-rpm",
+		"repodata/repomd.xml":       "application/xml",
+		"repodata/h-primary.xml.gz": "application/xml",
+		"repodata/h-primary.xml.xz": "application/xml",
+		"Packages/other":            "application/octet-stream",
+	} {
+		if got := p.ContentType(path); got != want {
+			t.Errorf("ContentType(%q)=%q want %q", path, got, want)
+		}
+	}
+
+	for flag, want := range map[int]string{
+		0x08 | 0x04: "GE",
+		0x02 | 0x04: "LE",
+		0x08:        "GT",
+		0x02:        "LT",
+		0x04:        "EQ",
+		0x00:        "",
+	} {
+		if got := rpmFlagString(flag); got != want {
+			t.Errorf("rpmFlagString(%d)=%q want %q", flag, got, want)
+		}
+	}
+
+	if firstGroup(nil) != "Unspecified" {
+		t.Error("empty groups should be Unspecified")
+	}
+	if firstGroup([]string{"System", "Base"}) != "System" {
+		t.Error("firstGroup should return the first")
+	}
+}
+
 func TestGenerateLocalIndexUnsupported(t *testing.T) {
 	if _, err := (&Provider{}).GenerateLocalIndex(context.Background(), fakeRPMReader{}, "r", "simple/"); err == nil {
 		t.Error("expected unsupported error")