gRPC

Load proto files, invoke all four streaming modes, and inspect metadata with Testnizer's native gRPC engine.

Testnizer uses @grpc/grpc-js and @grpc/proto-loader in the main process — no intermediary proxy, no port forwarding.

Multi-tab: Each gRPC tab loads its own proto file independently. Tabs do not share loaded services.

Opening a gRPC tab

Click + New → gRPC. The editor opens with a proto source picker and an empty service browser.

Proto source

Testnizer supports three ways to load a service definition:

1. File

Click Select .proto file and pick the file from disk. Testnizer parses the file (including any local imports from the same directory tree) and populates the Service and Method dropdowns.

If your proto imports other proto files by relative path, Testnizer resolves them from the same root directory — you don’t need to flatten the file.

2. URL

Paste a URL pointing to a .proto file. Testnizer fetches the file at send time and parses it exactly as if you had loaded it from disk. Useful for proto files hosted on a schema registry or internal artifact server.

3. Server reflection

If the server has the gRPC reflection service enabled, Testnizer can enumerate services without a proto file at all. Toggle Use server reflection in the connection panel and click Fetch services. Testnizer queries the reflection service using the grpc.reflection.v1 protocol with an automatic fallback to grpc.reflection.v1alpha for older servers. Reflection-loaded service definitions are cached locally.

Server address

Enter the target in host:port format:

api.internal:443
localhost:50051

Leading schemes are stripped automatically — grpc://, grpcs://, http://, and https:// all work. If no port is specified, Testnizer appends :443 when TLS is enabled and :80 when it is not.

TLS / mTLS is configured in the Connection panel:

Option	Description
Plaintext	Unencrypted gRPC (grpc://)
Server TLS	Verifies server certificate using the system trust store (or a custom CA you add)
Mutual TLS	Also sends a client certificate — pick from the project’s certificate store

For server TLS without a valid CA, you can add a self-signed CA certificate in Settings → Certificates and Testnizer will trust it for that hostname.

Service and method

After loading the proto, pick a service and a method from the dropdowns. Testnizer generates a JSON skeleton for the request message type with all fields present (populated with zero values). Fill in the fields you care about and clear the ones you don’t need — the serializer ignores null-valued optional fields.

Streaming modes

Unary

Single request, single response. Testnizer sends the request message and displays the response in the right pane.

Server-streaming

Single request, stream of responses. Testnizer holds the call open and appends each response message to the timeline as it arrives. A Cancel button appears while the stream is active; clicking it half-closes the client stream.

Client-streaming

Open a stream, send multiple request messages one by one (using the Send button for each), then click Finish sending to half-close and wait for the single response. A Cancel button appears during the call; clicking it half-closes the client stream immediately.

Bidirectional streaming

Both client and server stream simultaneously. Use the Send button to push request messages; server messages appear in the shared timeline. A Cancel button appears while streaming; clicking it half-closes the client stream. Click Close to finish the client half of the stream normally.

Metadata

The Metadata tab lets you add gRPC call metadata (equivalent to HTTP headers) as key-value pairs. Both request and response metadata are shown.

Common uses:

• authorization: Bearer {{token}}
• x-request-id: {{$randomUUID}}
• grpc-timeout: 30S

Request and response view

Request and response messages are shown as pretty-printed JSON (the protobufjs JSON representation). Enum values are shown by name, not number. bytes fields are shown as Base64.

For streaming calls, each message in the timeline is individually expandable.

Deadlines

Set a call deadline in the request settings (gear icon). Testnizer sends the grpc-timeout metadata header and cancels the call if the deadline is reached, showing a DEADLINE_EXCEEDED status.

Status codes

gRPC status codes (OK, CANCELLED, NOT_FOUND, UNAUTHENTICATED, etc.) appear in the status indicator above the response pane, colour-coded by severity:

• OK (0) → green
• CANCELLED (1), NOT_FOUND (5) → yellow
• INTERNAL (13), UNAVAILABLE (14), UNAUTHENTICATED (16), etc. → red

Environment variables

{{variable}} substitution works in the server address, metadata values, and JSON request body at send time.