# How to Test OmniRoute Implementation: Unit, Vitest, and Integration Testing Guide

> Learn how to test OmniRoute implementation using unit, Vitest, and integration tests. Ensure AI gateway correctness with Zod schemas, routing strategies, and provider resilience.

- Repository: [Diego Rodrigues de Sa e Souza/OmniRoute](https://github.com/diegosouzapw/OmniRoute)
- Tags: how-to-guide
- Published: 2026-09-12

---

**OmniRoute validates its AI gateway through a three-layer testing strategy—Unit tests for isolated logic, Vitest for streaming engines, and Integration/E2E tests for full request pipelines—that ensures correctness across Zod schemas, combo routing strategies, and provider resilience.**

Testing a multi-provider LLM gateway requires verifying everything from pure function logic to complex failover behavior across network boundaries. This guide explains how to test OmniRoute implementation using the repository's comprehensive test architecture, which splits validation across Node's native test runner, high-performance Vitest suites, and full-stack integration scenarios. Whether you're validating a new combo routing strategy in [`chatCore.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/chatCore.ts) or ensuring streaming resilience, OmniRoute's test harnesses provide the isolated environments and mocking utilities required for reliable continuous integration.

## OmniRoute's Three-Layer Testing Architecture

The repository organizes verification into three complementary layers, each targeting different aspects of the gateway's behavior.

**Unit tests** validate isolated functions, Zod schemas, and pure-logic modules using Node's native test runner. Execute these with:

```bash
npm run test:unit

```

**Vitest tests** exercise the streaming engine, combo routing algorithms, and MCP tools using the fast Vitest runner focused on the `open-sse` workspace. Run these with:

```bash
npm run test:vitest

```

**Integration and E2E tests** spin up the Next.js server (or MCP server) and execute end-to-end scenarios against real provider mocks. This layer includes live WebSocket tests, proxy health checks, and UI smoke tests via Playwright. Execute with:

```bash
npm run test:integration
npm run test:e2e

```

All test commands enforce the repository's quality-gate rules, failing CI on any regression.

## The Chat Pipeline Harness for Isolated Integration Testing

All integration tests build upon a **Chat Pipeline Harness** defined in [`tests/integration/_chatPipelineHarness.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/tests/integration/_chatPipelineHarness.ts). This harness wires together the request-validation, routing, and response-generation code paths without requiring live network access.

The harness creates an in-memory SQLite database, seeds provider connections, and patches `globalThis.fetch` with mock responses. This isolates tests from external network calls while still exercising the full request pipeline defined in [`open-sse/handlers/chatCore.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/open-sse/handlers/chatCore.ts).

Import and initialize the harness in any integration test:

```typescript
import { createChatPipelineHarness } from "./_chatPipelineHarness.ts";

const harness = await createChatPipelineHarness("combo-routing");

```

The harness leverages call-logging helpers from [`src/lib/usage/callLogs.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/src/lib/usage/callLogs.ts) to capture request metadata for assertions.

## Testing Combo Routing Strategies with the Priority Pattern

The following example from [`tests/integration/combo-routing-e2e.test.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/tests/integration/combo-routing-e2e.test.ts) demonstrates how to verify a **priority** combo strategy that sticks to the primary model while healthy:

```typescript
test("priority combo sticks to the primary model while healthy", async () => {
  await seedConnection("openai", { apiKey: "sk-openai-priority" });
  await seedConnection("claude", { apiKey: "sk-claude-priority" });
  await combosDb.createCombo({
    name: "router-priority-healthy",
    strategy: "priority",
    models: ["openai/gpt-4o-mini", "claude/claude-3-5-sonnet-20241022"],
  });

  const seenTargets = [];
  globalThis.fetch = async (url) => {
    seenTargets.push(String(url));
    return buildOpenAIResponse("Primary stayed active");
  };

  const first = await handleChat(
    buildRequest({ body: buildOpenAIChatBody("router-priority-healthy", "Route priority first") })
  );
  const second = await handleChat(
    buildRequest({ body: buildOpenAIChatBody("router-priority-healthy", "Route priority second") })
  );

  assert.equal(first.status, 200);
  assert.equal(second.status, 200);
  assert.equal(seenTargets.length, 2);
  assert.ok(seenTargets.every((t) => t.includes("/chat/completions")));
});

```

This test validates:

- **Connection seeding**: Populates provider tables via `seedConnection`
- **Combo creation**: Verifies the combo DB schema through `combosDb.createCombo`
- **Routing logic**: Exercises the `priority` strategy inside `handleChat` (located in [`open-sse/handlers/chatCore.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/open-sse/handlers/chatCore.ts))
- **Fallback behavior**: Confirms primary model usage when mocks return successful responses
- **Response validation**: Asserts HTTP status codes and upstream call counts

Similar integration tests exist for **round-robin**, **fallback-on-error**, and **sticky-round-robin** strategies within the `tests/integration/` directory.

## Running the Complete Test Suite

Execute the full verification workflow using npm scripts. First, install dependencies and initialize environment variables:

```bash
npm ci

```

Run specific test layers:

```bash

# Unit tests only

npm run test:unit

# Vitest suite (streaming, combo, MCP)

npm run test:vitest

# Integration tests (requires server spin-up)

npm run test:integration

# UI end-to-end tests with Playwright

npm run test:e2e

```

Verify coverage thresholds, which must remain at or above 60% across all metrics:

```bash
npm run test:coverage

```

Coverage regressions will abort the CI pipeline and must be resolved before merging.

## Debugging Failed Tests and Network Safety

When tests fail, the harness automatically prints the captured `fetchCalls` array and full request/response objects. Enable verbose logging for detailed trace output:

```bash
OMNIROUTE_LOG_LEVEL=debug npm run test:integration

```

Logging configuration resides in [`src/sse/utils/logger.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/src/sse/utils/logger.ts).

OmniRoute prevents accidental live network calls during testing through the **outbound SSRF guard** implemented in [`src/shared/network/outboundUrlGuard.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/src/shared/network/outboundUrlGuard.ts). To temporarily disable this guard for a specific test requiring real provider access, set the environment variable in the test's `beforeEach` hook:

```typescript
beforeEach(() => {
  process.env.OUTBOUND_SSRF_GUARD_ENABLED = "0";
});

```

## Continuous Integration Quality Gates

The CI pipeline executes a strict four-step sequence on every push to ensure code quality:

1. **`npm run lint`** — ESLint with strict `no-eval` and `no-explicit-any` rules
2. **`npm run check:docs-all`** — Validates generated documentation consistency
3. **`npm run test:unit` + `npm run test:vitest`** — Ensures core logic and streaming engines pass
4. **`npm run test:coverage`** — Enforces the 60% coverage gate

Failure at any stage blocks PR merging until resolved.

## Summary

- OmniRoute implements a **three-layer testing strategy** (Unit, Vitest, Integration/E2E) to validate logic, streaming engines, and full pipelines.
- The **Chat Pipeline Harness** in [`tests/integration/_chatPipelineHarness.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/tests/integration/_chatPipelineHarness.ts) provides isolated in-memory database and fetch mocking for integration tests.
- **Combo routing strategies** like priority and round-robin are tested against mocked provider responses in [`tests/integration/combo-routing-e2e.test.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/tests/integration/combo-routing-e2e.test.ts).
- All test commands respect **60% coverage thresholds** and strict quality gates that block CI on failure.
- The **SSR guard** ([`src/shared/network/outboundUrlGuard.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/src/shared/network/outboundUrlGuard.ts)) prevents accidental live network calls, with debug logging available via `OMNIROUTE_LOG_LEVEL=debug`.

## Frequently Asked Questions

### What is the Chat Pipeline Harness in OmniRoute?

The **Chat Pipeline Harness** is a test utility located in [`tests/integration/_chatPipelineHarness.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/tests/integration/_chatPipelineHarness.ts) that creates an isolated testing environment for integration tests. It initializes an in-memory SQLite database, seeds provider connection tables, and patches `globalThis.fetch` to intercept outbound requests. This allows developers to test the complete request pipeline—including routing logic in [`chatCore.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/chatCore.ts)—without making real network calls to LLM providers.

### How do I run only the unit tests for OmniRoute?

Execute `npm run test:unit` to run only the unit test suite. This command uses Node's native test runner to validate isolated functions, Zod schemas, and pure-logic modules without spinning up servers or databases. Unit tests complete quickly and are ideal for rapid feedback during development iterations.

### What code coverage threshold does OmniRoute enforce?

OmniRoute enforces a minimum **60% coverage** threshold across all metrics including statements, branches, functions, and lines. The `npm run test:coverage` command validates these thresholds, and any regression will fail the CI pipeline. This gate ensures that new features include adequate test coverage before merging into the main branch.

### How can I debug a failing combo routing test?

Set the environment variable `OMNIROUTE_LOG_LEVEL=debug` before running the test suite to enable verbose logging from [`src/sse/utils/logger.ts`](https://github.com/diegosouzapw/OmniRoute/blob/main/src/sse/utils/logger.ts). The Chat Pipeline Harness automatically captures the `fetchCalls` array and prints full request/response objects upon assertion failure. For tests requiring real provider validation, temporarily disable the SSRF guard by setting `process.env.OUTBOUND_SSRF_GUARD_ENABLED = "0"` in your test's `beforeEach` hook.