adding very simple tests for main calls

test/main.ts

@@ -4,21 +4,26 @@ import {
 } from 'chai';
 import 'mocha';
 import Reporter from '../src/reporter/reporter';
-import { NullLogger } from '../src/logger/null-logger';
+import {
+  NullLogger,
+} from '../src/logger/null-logger';
 
-const NOOPR: Reporter = () => {/* noop */};
+const NOOPR: Reporter = () => { /* noop */ };
+const ONE = 1;
 
 describe('main', () => {
   it('should be a function', () => {
     expect(main,).to.be.a('function',);
   },);
   it('can be called with 3 params', () => {
-    expect(() => main(1, 1, []),).to.not.throw;
+    expect(() => main(ONE, ONE, [],),).to.throw('Can\'t measure no tasks.',);
   },);
   it('can be called with 4 params', () => {
-    expect(() => main(1, 1, [], NOOPR),).to.not.throw;
+    expect(() => main(ONE, ONE, [], NOOPR,),)
+      .to.throw('Can\'t measure no tasks.',);
   },);
   it('can be called with 5 params', () => {
-    expect(() => main(1, 1, [], NOOPR, new NullLogger()),).to.not.throw;
+    expect(() => main(ONE, ONE, [], NOOPR, new NullLogger(),),)
+      .to.throw('Can\'t measure no tasks.',);
   },);
 },);