Demonstrate crash when using Truecolor methods and color is unsupported (#174)

fixture.js

@@ -0,0 +1,4 @@
+'use strict';
+const chalk = require('.');
+
+console.log(chalk.hex('#ff6159')('test'));

package.json

@@ -46,6 +46,7 @@
 	},
 	"devDependencies": {
 		"coveralls": "^2.11.2",
+		"execa": "^0.7.0",
 		"import-fresh": "^2.0.0",
 		"matcha": "^0.7.0",
 		"mocha": "*",

test.js

@@ -2,6 +2,7 @@
 const assert = require('assert');
 const importFresh = require('import-fresh');
 const resolveFrom = require('resolve-from');
+const execa = require('execa');
 
 // Spoof supports-color
 require.cache[resolveFrom(__dirname, 'supports-color')] = {
@@ -202,6 +203,13 @@ describe('chalk.level', () => {
 		assert.equal(chalk.level, 1);
 		chalk.level = oldLevel;
 	});
+
+	it('should disable colors if they are not supported', () => {
+		return execa('node', ['fixture'])
+			.then(result => {
+				assert.equal(result.stdout, 'test');
+			});
+	});
 });
 
 describe('chalk.enabled', () => {