Add coverage for math function fallbacks

test/fallback-functions.js

@@ -0,0 +1,38 @@
+/* global describe, it */
+
+'use strict';
+
+var assert = require('assert');
+var Parser = require('../dist/bundle').Parser;
+
+function assertCloseTo(actual, expected, delta) {
+  assert.ok(Math.abs(actual - expected) <= delta);
+}
+
+function withMissingMathFunctions(names, callback) {
+  var originals = {};
+  names.forEach(function (name) {
+    originals[name] = Math[name];
+    Math[name] = undefined;
+  });
+
+  try {
+    callback(new Parser());
+  } finally {
+    names.forEach(function (name) {
+      Math[name] = originals[name];
+    });
+  }
+}
+
+describe('Fallback math functions', function () {
+  it('uses internal fallbacks for expm1, log1p, and log2', function () {
+    withMissingMathFunctions(['expm1', 'log1p', 'log2'], function (parser) {
+      var delta = 1e-15;
+
+      assertCloseTo(parser.evaluate('expm1 2'), 6.38905609893065, delta);
+      assertCloseTo(parser.evaluate('log1p 9'), 2.302585092994046, delta);
+      assertCloseTo(parser.evaluate('log2 1024'), 10, delta);
+    });
+  });
+});