@bonniernews/wildcard-expect

A simple utility for extending Chai's expect with powerful wildcard matching, perfect for testing dynamic or partially known data structures in your applications. This library allows you to assert the shape and type of your data without needing to know the exact values of certain fields, such as IDs, timestamps, or generated tokens.

🚀 Installation

npm install --save-dev @bonniernews/wildcard-expect
# or
yarn add --dev @bonniernews/wildcard-expect

You'll also need to make sure Chai is set up in your test environment.

✨ Why Use It?

When testing API responses, database records, or complex object structures, you often encounter fields whose exact values are non-deterministic (e.g., UUIDs, timestamps, unique trace IDs). Standard expect assertions would fail if these values changed on each run.

@bonniernews/wildcard-expect solves this by providing "wildcard" placeholders. You define the expected type of a field, and the library handles the validation, ensuring your tests are robust and less brittle.

💡 Usage

Integrate wildcard-expect with your Chai assertions. The library provides an expect function that wraps Chai's, allowing you to use wildcards in your expected objects.

Basic Example

Let's say you're testing an API endpoint that returns a chat message object with a unique ID and a creation timestamp:

import wildcard from "@bonniernews/wildcard-expect"; // instead of import { expect } from "chai";

describe("Chat API", () => {
  it("should return a valid chat structure with dynamic fields", () => {
    wildcard.expect(responseBody).to.deep.equal({
      chatId: "some-chat-id-123", // Exact match
      replies: [
        {
          id: wildcard.uuid(), // Expect a valid UUID
          timestamp: wildcard.date(), // Expect a valid Date object or ISO date string
          role: "assistant",
          content: "Hello there!",
          metadata: {
            source: "AI",
            version: wildcard.number(), // Expect a number
            details: wildcard.string(), // Expect a string
          },
        },
        {
          id: wildcard.uuid(),
          timestamp: wildcard.date(),
          role: "user",
          content: "Hi!",
        },
      ],
      traceId: wildcard.traceid(), // Expect a valid trace ID
      url: wildcard.url(), // Expect a valid URL
    });
  });

  it("can be used with other chai methods like .property", () => {
    wildcard.expect(responseBody).to.have.property("chatId", "some-chat-id-123");
    wildcard.expect(responseBody.replies[0]).to.have.property("id", wildcard.uuid());
  });
});

Available Wildcard Types

You can use the following wildcard types:

• wildcard.any(): Matches any value.
• wildcard.string(): Matches any string.
• wildcard.number(): Matches any number.
• wildcard.boolean(): Matches any boolean.
• wildcard.object(): Matches any non-null object.
• wildcard.array(): Matches any array.
• wildcard.fn(): Matches any function.
• wildcard.uuid(): Matches a string that is a valid UUID (v1, v3, v4, v5).
• wildcard.date(): Matches a Date object or a string that can be parsed into a valid date (e.g., ISO 8601 string).
• wildcard.traceid(): Matches a string that is a valid trace ID (e.g., a 32-character hexadecimal string).
• wildcard.url(): Matches a string that is a valid URL.

🤝 Contributing

We welcome contributions! If you have suggestions for improvements, new wildcard types, or bug fixes, feel free to open an issue or submit a pull request.

📦 Publishing

To publish a new version of this library to npm:

Run npm run bump and push to main