diff --git a/tests/describe.test.js b/tests/describe.test.js
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+++ b/tests/describe.test.js
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+/*
+	Neonatal jaundice treatment threshold calculator
+	Copyright (C) 2024  Lee Yingtong Li
+	
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Affero General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+	
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Affero General Public License for more details.
+	
+	You should have received a copy of the GNU Affero General Public License
+	along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+// Import bilirubin_lib.js
+const fs = require('fs');
+eval(fs.readFileSync('src/bilirubin_lib.js').toString());
+
+const assert = require('node:assert');
+const { suite, test } = require('node:test');
+
+suite('Describe bilirubin result', () => {
+	const dateBirth = new Date(2024, 11, 24, 4, 20, 31, 415);
+	const dateMeasurement = new Date(2024, 11, 25, 4, 20, 31, 415);
+	const gestation = 38;
+	
+	test('Well below phototherapy threshold', () => {
+		const bilirubin = 20;
+		const expectedText = 'Bilirubin of 20 at 1 day, 0 hours is <span class="font-bold">180 below</span> the phototherapy threshold.';
+		const expectedColour = 'sky';
+		
+		let [d, result_text, text_colour, background_colour, accent_colour] = describeBilirubin(gestation, dateBirth, dateMeasurement, bilirubin);
+		
+		assert.equal(d, 1);
+		assert.equal(result_text, expectedText);
+		assert.equal(text_colour, 'text-' + expectedColour + '-800');
+		assert.equal(background_colour, 'bg-' + expectedColour + '-50');
+		assert.equal(accent_colour, 'border-' + expectedColour + '-400');
+	});
+	
+	test('Within 50 of phototherapy threshold', () => {
+		const bilirubin = 160;
+		const expectedText = 'Bilirubin of 160 at 1 day, 0 hours is <span class="font-bold">40 below</span> the phototherapy threshold.';
+		const expectedColour = 'yellow';
+		
+		let [d, result_text, text_colour, background_colour, accent_colour] = describeBilirubin(gestation, dateBirth, dateMeasurement, bilirubin);
+		
+		assert.equal(d, 1);
+		assert.equal(result_text, expectedText);
+		assert.equal(text_colour, 'text-' + expectedColour + '-800');
+		assert.equal(background_colour, 'bg-' + expectedColour + '-50');
+		assert.equal(accent_colour, 'border-' + expectedColour + '-400');
+	});
+	
+	test('Above phototherapy threshold', () => {
+		const bilirubin = 220;
+		const expectedText = 'Bilirubin of 220 at 1 day, 0 hours is <span class="font-bold">20 above</span> the phototherapy threshold, 80 below the exchange transfusion threshold.';
+		const expectedColour = 'orange';
+		
+		let [d, result_text, text_colour, background_colour, accent_colour] = describeBilirubin(gestation, dateBirth, dateMeasurement, bilirubin);
+		
+		assert.equal(d, 1);
+		assert.equal(result_text, expectedText);
+		assert.equal(text_colour, 'text-' + expectedColour + '-800');
+		assert.equal(background_colour, 'bg-' + expectedColour + '-50');
+		assert.equal(accent_colour, 'border-' + expectedColour + '-400');
+	});
+	
+	test('Above exchange transfusion threshold', () => {
+		const bilirubin = 350;
+		const expectedText = 'Bilirubin of 350 at 1 day, 0 hours is 50 above the <span class="font-bold">exchange transfusion</span> threshold.';
+		const expectedColour = 'red';
+		
+		let [d, result_text, text_colour, background_colour, accent_colour] = describeBilirubin(gestation, dateBirth, dateMeasurement, bilirubin);
+		
+		assert.equal(d, 1);
+		assert.equal(result_text, expectedText);
+		assert.equal(text_colour, 'text-' + expectedColour + '-800');
+		assert.equal(background_colour, 'bg-' + expectedColour + '-50');
+		assert.equal(accent_colour, 'border-' + expectedColour + '-400');
+	});
+});