Migrating from Chai to Tripwire

This guide helps you upgrade your codebase from Chai to Tripwire, using the Chai 5 assert shim or by fully adopting Tripwire’s native assertion APIs. It is designed for both human readers and GitHub Copilot-assisted migrations.

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1. Overview

Tripwire provides a robust assertion library for Node, browser, and worker environments, with a Chai 5 assert compatibility shim for easy migration.

Migration Paths

Chai API	Migration Option	Effort
assert	Use @nevware21/tripwire-chai shim	Minimal - import change only
assert	Use @nevware21/tripwire directly	Low - APIs are similar (some naming differences, see section 5)
expect	Use @nevware21/tripwire expect	Medium - syntax differences
should	Use @nevware21/tripwire expect	Medium - rewrite required

Note: There is no shim for Chai’s expect or should APIs. If you use these, you must migrate to Tripwire’s native expect API.

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2. Using the Chai 5 Assert Shim

Install Tripwire and the Shim

npm install @nevware21/tripwire @nevware21/tripwire-chai

Update Imports

Replace Chai imports like:

const assert = require('chai').assert;
// or
import { assert } from 'chai';

With:

import { assert } from '@nevware21/tripwire-chai';

Supported APIs

• The shim supports most Chai 5 assert methods (see README).
• Some advanced Chai plugins or custom assertions may require manual migration.

Example

Before:

import { assert } from 'chai';
assert.equal(foo, 42);
assert.isObject(bar);

After:

import { assert } from '@nevware21/tripwire-chai';
assert.equal(foo, 42);
assert.isObject(bar);

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3. Migrating Chai expect to Tripwire

If you use Chai’s expect API, you must migrate to Tripwire’s native expect. There is no shim for this API.

Update Imports

- import { expect } from 'chai';
+ import { expect } from '@nevware21/tripwire';

Chai expect → Tripwire expect Mappings

Most Chai expect chains translate directly to Tripwire:

Note: Tripwire type checks are function calls (e.g. expect(x).to.be.a.string()), and NaN/finite are nan()/finite() functions.

Chai expect	Tripwire expect
expect(x).to.equal(y)	expect(x).to.equal(y)
expect(x).to.deep.equal(y)	expect(x).to.deep.equal(y)
expect(x).to.be.true	expect(x).to.be.true()
expect(x).to.be.false	expect(x).to.be.false()
expect(x).to.be.null	expect(x).to.be.null()
expect(x).to.be.undefined	expect(x).to.be.undefined()
expect(x).to.be.a('string')	expect(x).to.be.a.string()
expect(x).to.be.an('array')	expect(x).to.be.an.array()
expect(x).to.be.instanceOf(Foo)	expect(x).to.be.instanceOf(Foo)
expect(x).to.have.property('y')	expect(x).to.have.property('y')
expect(x).to.have.lengthOf(3)	expect(x).to.have.lengthOf(3)
expect(x).to.include(y)	expect(x).to.include(y)
expect(x).to.contain(y)	expect(x).to.contain(y)
expect(fn).to.throw()	expect(fn).to.throw()
expect(fn).to.throw(Error)	expect(fn).to.throw(Error)
expect(fn).to.not.throw()	expect(fn).to.not.throw()
expect(x).to.be.above(5)	expect(x).to.be.above(5)
expect(x).to.be.below(10)	expect(x).to.be.below(10)
expect(x).to.be.at.least(5)	expect(x).to.be.at.least(5)
expect(x).to.be.at.most(10)	expect(x).to.be.at.most(10)
expect(x).to.be.within(5, 10)	expect(x).to.be.within(5, 10)
expect(x).to.match(/pattern/)	expect(x).to.match(/pattern/)
expect(x).to.have.members([1,2])	expect(x).to.include.sameMembers([1,2])
expect(x).to.have.keys('a', 'b')	expect(x).to.have.all.keys('a', 'b')
expect(x).to.be.empty	expect(x).to.be.empty()
expect(x).to.be.ok	expect(x).to.be.ok()
expect(x).to.exist	expect(x).to.exist()
expect(x).to.be.NaN	expect(x).to.be.nan()
expect(x).to.be.finite	expect(x).to.be.finite()

Strict equality note: Chai’s expect(x).to.equal(y) already uses strict equality. In Tripwire, you can force strict equality in the chain with expect(x).to.strictly.equal(y).

Example Migration

Before (Chai expect):

import { expect } from 'chai';

expect(result).to.be.an('object');
expect(result).to.have.property('name').that.equals('test');
expect(items).to.be.an('array').with.lengthOf(3);
expect(fn).to.throw(TypeError, /invalid/);

After (Tripwire expect):

import { expect } from '@nevware21/tripwire';

expect(result).to.be.an.object();
expect(result).to.have.property('name').that.equals('test');
expect(items).to.be.an.array();
expect(items).to.have.lengthOf(3);
expect(fn).to.throw(TypeError, /invalid/);

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4. Migrating Chai should to Tripwire

If you use Chai’s should API, you must rewrite using Tripwire’s expect. The should style is not supported.

Example Migration

Before (Chai should):

require('chai').should();

foo.should.be.a('string');
foo.should.equal('bar');
foo.should.have.lengthOf(3);

After (Tripwire expect):

import { expect } from '@nevware21/tripwire';

expect(foo).to.be.a.string();
expect(foo).to.equal('bar');
expect(foo).to.have.lengthOf(3);

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5. Full Migration from Chai assert to Tripwire

Update Imports

Replace Chai imports with Tripwire:

import { assert, expect } from '@nevware21/tripwire';

Refactor Assertions

Tripwire supports both assert and expect styles. The expect API is more expressive and recommended for new code.

Common Mappings

| Chai (assert) | Tripwire (assert) | Tripwire (expect) | |————————|—————————|———————————-| | assert.equal(a, b) | assert.equal(a, b) | expect(a).to.equal(b) | | assert.strictEqual(a, b) | assert.strictEqual(a, b) | expect(a).to.strictly.equal(b) | | assert.deepEqual(a, b) | assert.deepEqual(a, b) | expect(a).to.deep.equal(b) | | assert.isTrue(val) | assert.isTrue(val) | expect(val).to.be.true() | | assert.isFalse(val) | assert.isFalse(val) | expect(val).to.be.false() | | assert.isNull(val) | assert.isNull(val) | expect(val).to.be.null() | | assert.isUndefined(val)| assert.isUndefined(val) | expect(val).to.be.undefined() | | assert.isObject(obj) | assert.isObject(obj) | expect(obj).to.be.an.object() | | assert.isArray(arr) | assert.isArray(arr) | expect(arr).to.be.an.array() | | assert.isString(str) | assert.isString(str) | expect(str).to.be.a.string() | | assert.isNumber(num) | assert.isNumber(num) | expect(num).to.be.a.number() | | assert.isFunction(fn) | assert.isFunction(fn) | expect(fn).to.be.a.function() | | assert.throws(fn) | assert.throws(fn) | expect(fn).to.throw() | | assert.doesNotThrow(fn)| assert.doesNotThrow(fn) | expect(fn).to.not.throw() | | assert.include(arr, v) | assert.includes(arr, v) | expect(arr).to.include(v) | | assert.property(o, k) | assert.hasProperty(o, k) | expect(o).to.have.property(k) | | assert.lengthOf(a, n) | assert.lengthOf(a, n) | expect(a).to.have.lengthOf(n) |

Example Migration

Before (Chai):

import { assert } from 'chai';
assert.deepEqual(foo, { a: 1 });
assert.isFalse(bar);

After (Tripwire):

import { expect } from '@nevware21/tripwire';
expect(foo).to.deep.equal({ a: 1 });
expect(bar).to.be.false();

Remove Chai from Dependencies

• Remove chai and related plugins from your package.json.
• Ensure all tests pass in Node, browser, and worker environments.

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6. Migration with Copilot

GitHub Copilot can help automate migration. Use these prompts based on your Chai API:

For Chai assert → Tripwire shim (minimal changes)

Replace all 'chai' imports with '@nevware21/tripwire-chai' keeping assert usage unchanged.

For Chai assert → Tripwire expect (full migration)

Convert all Chai assert.* calls to Tripwire expect style. For example:
- assert.equal(a, b) → expect(a).to.equal(b)
- assert.isTrue(x) → expect(x).to.be.true()
- assert.throws(fn) → expect(fn).to.throw()

For Chai expect → Tripwire expect

Migrate Chai expect assertions to Tripwire. Update imports from 'chai' to '@nevware21/tripwire'.
Note: Most expect chains are identical, but check instanceof vs instanceOf.

For Chai should → Tripwire expect

Convert Chai should-style assertions to Tripwire expect. For example:
- foo.should.equal('bar') → expect(foo).to.equal('bar')
- foo.should.be.a('string') → expect(foo).to.be.a.string()
Remove the should() initialization call.

Tips for Copilot Migration

• Review suggestions for edge cases or custom assertions
• Test in all environments (Node, browser, worker) after migration
• For Chai plugins, rewrite using Tripwire’s expect or custom helpers

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7. Additional Notes

• Tripwire is ES5-compatible and works in all major JS environments.
• For unsupported Chai plugins, rewrite using Tripwire’s expect or custom helpers.
• See Tripwire API docs for full details.

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8. References

• Tripwire GitHub
• Tripwire Chai Shim
• Tripwire API Docs
• Chai Migration Guide

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For questions or issues, open an issue on GitHub.