Add Pdfkiwi constructor tests

test/specs/pdfkiwi.test.js

@@ -1,4 +1,21 @@
+const expect  = require('chai').expect;
 const Pdfkiwi = require('../../src/pdfkiwi');
 
 describe('Pdfkiwi', () => {
+    describe('constructor', () => {
+        it('should throw an error when called with missing API credentials', () => {
+            const _wrapCall = (...args) => (
+                () => { new Pdfkiwi(...args); } // eslint-disable-line no-new
+            );
+
+            expect(_wrapCall('foo', 'bar')).to.not.throw(/Incomplete Pdf\.kiwi API credentials\./);
+
+            expect(_wrapCall()).to.throw(Error, /Incomplete Pdf\.kiwi API credentials\./);
+            ['', null, 0].forEach((wrongArg) => {
+                expect(_wrapCall(wrongArg, wrongArg)).to.throw(Error, /Incomplete Pdf\.kiwi API credentials\./);
+                expect(_wrapCall('foo', wrongArg)).to.throw(Error, /Incomplete Pdf\.kiwi API credentials\./);
+                expect(_wrapCall(wrongArg, 'bar')).to.throw(Error, /Incomplete Pdf\.kiwi API credentials\./);
+            });
+        });
+    });
 });