Testing with a local mock server

httptest.Server can simulate a model service locally. Without a real account or external network access, a test can cover request serialization, streaming response parsing, and final message assembly.

The test below simulates an OpenAI Chat Completions SSE response. Save it as completion_test.go in a Go package that uses llm.

Complete test

package myapp_test

import (
    "context"
    "io"
    "net/http"
    "net/http/httptest"
    "testing"

    "github.com/ktsoator/or/llm"
    _ "github.com/ktsoator/or/llm/openai"
)

func TestCompletion(t *testing.T) {
    server := httptest.NewServer(http.HandlerFunc(
        func(w http.ResponseWriter, r *http.Request) {
            if r.URL.Path != "/v1/chat/completions" {
                t.Fatalf("path = %q", r.URL.Path)
            }
            w.Header().Set("Content-Type", "text/event-stream")
            io.WriteString(w, `data: {"choices":[{"index":0,"delta":{"content":"hi"},"finish_reason":null}]}`+"\n\n")
            io.WriteString(w, `data: {"choices":[{"index":0,"delta":{},"finish_reason":"stop"}]}`+"\n\n")
            io.WriteString(w, "data: [DONE]\n\n")
        }))
    defer server.Close()

    model := llm.Model{
        ID: "test-model", Provider: "test",
        Protocol: llm.ProtocolOpenAICompletions,
        BaseURL: server.URL + "/v1", MaxTokens: 100,
    }
    message, err := llm.Complete(context.Background(), model,
        llm.Prompt("hello"), llm.StreamOptions{APIKey: "test"})
    if err != nil {
        t.Fatal(err)
    }
    if got := message.Text(); got != "hi" {
        t.Fatalf("text = %q, want hi", got)
    }
    if message.StopReason != llm.StopReasonStop {
        t.Fatalf("stop = %q", message.StopReason)
    }
}

Run it:

go test ./...

The example API key satisfies request validation and is sent only to the local test server.

Additional paths to cover

• Inspect request JSON to assert tools, system prompts, reasoning options, and headers.
• Emit tool_calls first and a final answer on the second request to test a complete tool loop.
• Emit error status and malformed SSE to verify partial messages and error policy.
• Test Stream cancellation and continue receiving until channel close to detect goroutine leaks.
• Use a custom client and independent registries when testing custom adapters or provider overrides, avoiding package-global cross-test state.

Test scope

Local mock tests validate application logic and protocol translation. They do not validate authentication, rate limits, field differences, or live behavior of a real model service. Keep a small credentialed integration suite for model services used in production.