Added unit tests

CONTRIBUTING.md

@@ -3,3 +3,7 @@
 ## Manual testing
 
 To test the plugin manually, run `npm start`. This command builds the plugin and serves it up along with a basic map webpage on a local Web server.
+
+## Automated testing
+
+There are a number of test cases for basic and edge cases. Run `npm test`.

index.js

@@ -100,8 +100,14 @@ function constrainFilterByDate(filter, decimalYear) {
   return dateFilter;
 }
 
-if (window.maplibregl) {
+if (typeof window !== 'undefined' && 'maplibregl' in window) {
   maplibregl.Map.prototype.filterByDate = function (date) {
     filterByDate(this, date);
   };
+} else if (typeof module !== 'undefined') {
+  module.exports = {
+    filterByDate: filterByDate,
+    decimalYearFromDate: decimalYearFromDate,
+    dateFromISODate: dateFromISODate,
+  };
 }

index.spec.mjs

@@ -0,0 +1,38 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+
+import {
+  dateFromISODate,
+  decimalYearFromDate,
+} from './index.js';
+
+describe('dateFromISODate', () => {
+  it('should convert date strings to Date objects', () => {
+    assert.equal(+dateFromISODate('2013-01-01'), +new Date('2013-01-01'));
+    assert.equal(+dateFromISODate('2013-04-14'), +new Date('2013-04-14'));
+    assert.equal(+dateFromISODate('2013-12-31'), +new Date('2013-12-31'));
+  });
+
+  it('should support BCE dates', () => {
+    assert.equal(+dateFromISODate('0001-01-01'), +new Date('0001-01-01'));
+    assert.equal(+dateFromISODate('0000-01-01'), +new Date('0000-01-01'));
+    assert.equal(+dateFromISODate('-0000-01-01'), +new Date('0000-01-01'));
+    assert.equal(+dateFromISODate('-0001-01-01'), +new Date('-000001-01-01'));
+    assert.equal(+dateFromISODate('-9999-01-01'), +new Date('-009999-01-01'));
+  });
+});
+
+describe('decimalYearFromDate', () => {
+  it('should convert date objects to decimal years', () => {
+    assert.equal(decimalYearFromDate(new Date('2013-01-01')), 2013);
+    assert.equal(+decimalYearFromDate(new Date('2013-04-14')).toFixed(5), 2013.28219);
+    assert.equal(+decimalYearFromDate(new Date('2013-12-31')).toFixed(5), 2013.99726);
+  });
+
+  it('should support BCE dates', () => {
+    assert.equal(decimalYearFromDate(new Date('0001-01-01')), 1);
+    assert.equal(decimalYearFromDate(new Date('0000-01-01')), 0);
+    assert.equal(decimalYearFromDate(new Date('-000001-01-01')), -1);
+    assert.equal(decimalYearFromDate(new Date('-009999-01-01')), -9999);
+  });
+});

package.json

@@ -7,7 +7,7 @@
     "build": "esbuild index.js --bundle --outdir=dist",
     "clean": "shx rm -rf dist build",
     "start": "shx cp -r example dist && open 'http://127.0.0.1:8000/example/#map=15/29.9599/-90.0676&date=1900-01-01' && esbuild index.js --bundle --outdir=dist --servedir=dist --watch",
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "node --import ./test/setup.mjs --test 'index.spec.mjs'"
   },
   "repository": {
     "type": "git",

test/setup.mjs

@@ -0,0 +1,3 @@
+import { register } from 'node:module';
+
+