Add tests for canonicalUrl filter

test/lib/filters/canonical-url.js

@@ -0,0 +1,33 @@
+const assert = require('assert/strict')
+const { describe, it } = require('node:test')
+const nunjucks = require('nunjucks')
+const canonicalUrl = require('../../../lib/filters/canonical-url.js')
+
+describe('canonicalUrl filter', () => {
+  const ctx = { options: { url: 'https://example.com' } }
+  const env = new nunjucks.Environment()
+  env.addFilter('canonicalUrl', canonicalUrl)
+
+  it('Returns given path if no site URL defined', () => {
+    const result = env.renderString('{{ "/path" | canonicalUrl }}', {
+      options: {}
+    })
+
+    assert.equal(result, '/path')
+  })
+
+  it('Returns external URL if doesn’t share hostname with site URL', () => {
+    const result = env.renderString(
+      '{{ "http://foo.bar" | canonicalUrl }}',
+      ctx
+    )
+
+    assert.equal(result, 'http://foo.bar')
+  })
+
+  it('Gets canonical site URL with resolved path', () => {
+    const result = env.renderString('{{ "/path" | canonicalUrl }}', ctx)
+
+    assert.equal(result, 'https://example.com/path')
+  })
+})