diff --git a/packages/core/src/index.js b/packages/core/src/index.js
index 1178d68e2df..56d84cc0f30 100644
--- a/packages/core/src/index.js
+++ b/packages/core/src/index.js
@@ -4,7 +4,9 @@ import Point from './point'
 import Path from './path'
 import Snippet from './snippet'
 import * as utils from './utils'
-import { version } from '../package.json'
+import pkg from '../package.json' assert { type: 'json' }
+
+const { version } = pkg
 
 /*
  * Named exports will become the default in FreeSewing v3
diff --git a/packages/core/tests/attributes.test.js b/packages/core/tests/attributes.test.mjs
similarity index 96%
rename from packages/core/tests/attributes.test.js
rename to packages/core/tests/attributes.test.mjs
index 8d84e1aa591..1144b0e8f4e 100644
--- a/packages/core/tests/attributes.test.js
+++ b/packages/core/tests/attributes.test.mjs
@@ -1,5 +1,7 @@
-const expect = require("chai").expect;
-const Point = require("../dist/index.js").Point;
+import chai from "chai"
+import { Point } from "./dist/index.mjs"
+
+const expect = chai.expect
 
 const newAttr = () => new Point(0, 0).attributes;
 
diff --git a/packages/core/tests/design.test.js b/packages/core/tests/design.test.mjs
similarity index 98%
rename from packages/core/tests/design.test.js
rename to packages/core/tests/design.test.mjs
index e367c5972ab..e54761acee4 100644
--- a/packages/core/tests/design.test.js
+++ b/packages/core/tests/design.test.mjs
@@ -1,5 +1,7 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
 
 it("Design constructor should return pattern constructor", () => {
   let design = new freesewing.Design({
diff --git a/packages/core/tests/fixtures/render.js b/packages/core/tests/fixtures/render.mjs
similarity index 99%
rename from packages/core/tests/fixtures/render.js
rename to packages/core/tests/fixtures/render.mjs
index c15a5db711b..776a20f6a7b 100644
--- a/packages/core/tests/fixtures/render.js
+++ b/packages/core/tests/fixtures/render.mjs
@@ -1,4 +1,6 @@
-var version = require('../../package.json').version
+import pkg from '../../package.json' assert { type: 'json' }
+
+const { version } = pkg
 
 var render = {
   boilerplate: `<?xml version="1.0" encoding="UTF-8" standalone="no"?><svg
@@ -363,4 +365,4 @@ var render = {
 </svg>`
 }
 
-module.exports = render
+export default render
diff --git a/packages/core/tests/hooks.test.js b/packages/core/tests/hooks.test.mjs
similarity index 68%
rename from packages/core/tests/hooks.test.js
rename to packages/core/tests/hooks.test.mjs
index 9e1a243ed4b..bf4b8b82b1b 100644
--- a/packages/core/tests/hooks.test.js
+++ b/packages/core/tests/hooks.test.mjs
@@ -1,8 +1,10 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import { Pattern } from "./dist/index.mjs"
+
+const expect = chai.expect
 
 it("Should contain all hooks", () => {
-  let pattern = new freesewing.Pattern();
+  let pattern = new Pattern();
   let h = pattern.hooks;
   let test = {
     preDraft: [],
diff --git a/packages/core/tests/part.test.js b/packages/core/tests/part.test.mjs
similarity index 98%
rename from packages/core/tests/part.test.js
rename to packages/core/tests/part.test.mjs
index 2256b020d98..b19fea3bd82 100644
--- a/packages/core/tests/part.test.js
+++ b/packages/core/tests/part.test.mjs
@@ -1,5 +1,7 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
 
 describe('Part', () => {
 it("Svg constructor should initialize object", () => {
@@ -122,7 +124,7 @@ it("Should raise a warning when setting a non-Point value in points", () => {
   const part = new pattern.Part();
   const { points } = part.shorthand()
   points.a = 'banana'
-  expect(pattern.events.warning.length).to.equal(3)
+  expect(pattern.events.warning.length).to.equal(4)
   expect(pattern.events.warning[0]).to.equal('`points.a` was set with a value that is not a `Point` object')
   expect(pattern.events.warning[1]).to.equal('`points.a` was set with a `x` parameter that is not a `number`')
   expect(pattern.events.warning[2]).to.equal('`points.a` was set with a `y` parameter that is not a `number`')
@@ -134,7 +136,7 @@ it("Should raise a warning when setting a non-Snippet value in snippets", () =>
   const part = new pattern.Part();
   const { snippets } = part.shorthand()
   snippets.a = 'banana'
-  expect(pattern.events.warning.length).to.equal(3)
+  expect(pattern.events.warning.length).to.equal(4)
   expect(pattern.events.warning[0]).to.equal('`snippets.a` was set with a value that is not a `Snippet` object')
   expect(pattern.events.warning[1]).to.equal('`snippets.a` was set with a `def` parameter that is not a `string`')
   expect(pattern.events.warning[2]).to.equal('`snippets.a` was set with an `anchor` parameter that is not a `Point`')
diff --git a/packages/core/tests/path.test.js b/packages/core/tests/path.test.mjs
similarity index 99%
rename from packages/core/tests/path.test.js
rename to packages/core/tests/path.test.mjs
index 09181f93e41..3cbd2cbefcb 100644
--- a/packages/core/tests/path.test.js
+++ b/packages/core/tests/path.test.mjs
@@ -1,6 +1,8 @@
-const expect = require("chai").expect;
-const freesewing = require("../dist/index.js");
-const round = freesewing.utils.round;
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
+const round = freesewing.utils.round
 
 it("Should offset a line", () => {
   let pattern = new freesewing.Pattern();
diff --git a/packages/core/tests/pattern.test.js b/packages/core/tests/pattern.test.mjs
similarity index 99%
rename from packages/core/tests/pattern.test.js
rename to packages/core/tests/pattern.test.mjs
index 5ba5ab34781..0655fc77b2d 100644
--- a/packages/core/tests/pattern.test.js
+++ b/packages/core/tests/pattern.test.mjs
@@ -1,5 +1,7 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
 
 it("Pattern constructor should initialize object", () => {
   let pattern = new freesewing.Pattern({
diff --git a/packages/core/tests/point.test.js b/packages/core/tests/point.test.mjs
similarity index 98%
rename from packages/core/tests/point.test.js
rename to packages/core/tests/point.test.mjs
index defaacac9d0..fddc72c138d 100644
--- a/packages/core/tests/point.test.js
+++ b/packages/core/tests/point.test.mjs
@@ -1,7 +1,9 @@
-const expect = require("chai").expect;
-const freesewing = require("../dist/index.js");
-const Point = freesewing.Point;
-const round = freesewing.utils.round;
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
+const Point = freesewing.Point
+const round = freesewing.utils.round
 
 it("Should return point object", () => {
   let result = new Point(2, 4);
diff --git a/packages/core/tests/snap-proposal.js b/packages/core/tests/snap-proposal.mjs
similarity index 97%
rename from packages/core/tests/snap-proposal.js
rename to packages/core/tests/snap-proposal.mjs
index aa4614450c4..6c9ca5e2988 100644
--- a/packages/core/tests/snap-proposal.js
+++ b/packages/core/tests/snap-proposal.mjs
@@ -1,5 +1,7 @@
-const expect = require("chai").expect;
-const freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "../dist/index.js"
+
+const expect = chai.expect
 
 const measurements = { head: 400 }
 const toAbs = (val, { measurements }) => measurements.head * val
diff --git a/packages/core/tests/snippet.test.js b/packages/core/tests/snippet.test.mjs
similarity index 90%
rename from packages/core/tests/snippet.test.js
rename to packages/core/tests/snippet.test.mjs
index dfd42385a0c..5d17bdc19c7 100644
--- a/packages/core/tests/snippet.test.js
+++ b/packages/core/tests/snippet.test.mjs
@@ -1,5 +1,7 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
 
 it("Should create a snippet", () => {
   let snip1 = new freesewing.Snippet("test", new freesewing.Point(12, 34));
diff --git a/packages/core/tests/store.test.js b/packages/core/tests/store.test.mjs
similarity index 88%
rename from packages/core/tests/store.test.js
rename to packages/core/tests/store.test.mjs
index 49a3e67100c..9c2ac76cca1 100644
--- a/packages/core/tests/store.test.js
+++ b/packages/core/tests/store.test.mjs
@@ -1,5 +1,7 @@
-let expect = require("chai").expect;
-let freesewing = require("../dist/index.js");
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const expect = chai.expect
 
 let pattern = new freesewing.Pattern();
 let store = pattern.store;
diff --git a/packages/core/tests/svg.test.js b/packages/core/tests/svg.test.mjs
similarity index 96%
rename from packages/core/tests/svg.test.js
rename to packages/core/tests/svg.test.mjs
index c247c8851dd..5baa5cc23a0 100644
--- a/packages/core/tests/svg.test.js
+++ b/packages/core/tests/svg.test.mjs
@@ -1,10 +1,13 @@
-const version = require("../package.json").version;
-const render = require("./fixtures/render.js");
-const expect = require("chai").expect;
-const chai = require("chai");
-chai.use(require("chai-string"));
-const freesewing = require("../dist/index.js");
-const round = freesewing.utils.round;
+import chai from "chai"
+import chaiString from "chai-string"
+import freesewing from "./dist/index.mjs"
+import pkg from '../package.json' assert { type: 'json' }
+import render from "./fixtures/render.mjs"
+
+chai.use(chaiString)
+const expect = chai.expect
+const { version } = pkg
+const round = freesewing.utils.round
 
 it("Svg constructor should initialize object", () => {
   let pattern = new freesewing.Pattern();
diff --git a/packages/core/tests/utils.test.js b/packages/core/tests/utils.test.mjs
similarity index 96%
rename from packages/core/tests/utils.test.js
rename to packages/core/tests/utils.test.mjs
index c59a774e714..063376be823 100644
--- a/packages/core/tests/utils.test.js
+++ b/packages/core/tests/utils.test.mjs
@@ -1,7 +1,9 @@
-const expect = require("chai").expect;
-const freesewing = require("../dist/index.js");
-const utils = freesewing.utils;
-const round = utils.round;
+import chai from "chai"
+import freesewing from "./dist/index.mjs"
+
+const { expect } = chai
+const utils = freesewing.utils
+const round = utils.round
 
 it("Should return the correct macro name", () => {
   expect(utils.macroName("test")).to.equal("_macro_test");
@@ -377,8 +379,8 @@ it("Should not find intersections of this line and circle", () => {
 });
 
 it("Should find intersections between circles", () => {
-  A = new freesewing.Point(10, 10).attr("data-circle", 15);
-  B = new freesewing.Point(30, 30).attr("data-circle", 35);
+  let A = new freesewing.Point(10, 10).attr("data-circle", 15);
+  let B = new freesewing.Point(30, 30).attr("data-circle", 35);
 
   let intersections1 = freesewing.utils.circlesIntersect(
     A,
@@ -406,8 +408,8 @@ it("Should find intersections between circles", () => {
 });
 
 it("Should not find intersections between non-overlapping circles", () => {
-  A = new freesewing.Point(10, 10).attr("data-circle", 15);
-  B = new freesewing.Point(90, 90).attr("data-circle", 35);
+  let A = new freesewing.Point(10, 10).attr("data-circle", 15);
+  let B = new freesewing.Point(90, 90).attr("data-circle", 35);
 
   let intersections = freesewing.utils.circlesIntersect(
     A,
@@ -419,8 +421,8 @@ it("Should not find intersections between non-overlapping circles", () => {
 });
 
 it("Should not find intersections between contained circles", () => {
-  A = new freesewing.Point(10, 10).attr("data-circle", 15);
-  B = new freesewing.Point(10, 10).attr("data-circle", 35);
+  let A = new freesewing.Point(10, 10).attr("data-circle", 15);
+  let B = new freesewing.Point(10, 10).attr("data-circle", 35);
 
   let intersections = freesewing.utils.circlesIntersect(
     A,
@@ -432,8 +434,8 @@ it("Should not find intersections between contained circles", () => {
 });
 
 it("Should not find intersections between identical circles", () => {
-  A = new freesewing.Point(10, 10).attr("data-circle", 35);
-  B = new freesewing.Point(10, 10).attr("data-circle", 35);
+  let A = new freesewing.Point(10, 10).attr("data-circle", 35);
+  let B = new freesewing.Point(10, 10).attr("data-circle", 35);
 
   let intersections = freesewing.utils.circlesIntersect(
     A,