test: fail fast on missing VCR cassettes by converting errors to 404

If a VCR cassette or a specific interaction is missing, the OSV client
would previously retry the request 4 times with exponential backoff,
causing significant delays in test execution (over 20 seconds).

This change wraps the VCR client transport in tests to intercept the
"requested interaction not found" error and convert it to a "404 Not Found"
response. Since the OSV client does not retry on 404 status codes, this
allows tests to fail immediately (~0.02s) on missing cassettes/interactions
while still preserving retry behavior for genuine transient network errors.

- Implemented vcrErrorWrappingTransport in internal/testcmd/vcr.go
- Wrapped the VCR client transport in InsertCassette

Author: another-rex

cmd/osv-scanner/internal/testcmd/vcr.go

@@ -173,7 +173,10 @@ func InsertCassette(t *testing.T) *http.Client {
 		sortCassetteInteractions(t, path)
 	})
 
-	return r.GetDefaultClient()
+	client := r.GetDefaultClient()
+	client.Transport = &vcrErrorWrappingTransport{wrapper: client.Transport}
+
+	return client
 }
 
 // sortCassetteInteractions reorders the interactions in the given cassette, based
@@ -255,3 +258,23 @@ func matchBody(r *http.Request, i cassette.Request) bool {
 
 	return true
 }
+
+type vcrErrorWrappingTransport struct {
+	wrapper http.RoundTripper
+}
+
+func (t *vcrErrorWrappingTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	resp, err := t.wrapper.RoundTrip(req)
+	if err != nil && strings.Contains(err.Error(), "requested interaction not found") {
+		// Convert VCR error to a 404 response to avoid retries by the client
+		return &http.Response{
+			StatusCode: http.StatusNotFound,
+			Status:     "404 Not Found (VCR: requested interaction not found)",
+			Body:       io.NopCloser(strings.NewReader("VCR: requested interaction not found")),
+			Header:     make(http.Header),
+			Request:    req,
+		}, nil
+	}
+
+	return resp, err
+}