Bail out with an error, if non-existent entry point is provided

For lookupStrategy "multipleIdOrName", we should bail out wit an error
if one of the provided entrypoints does not exist.

lib/runner/extract-runnable-items.js

@@ -198,9 +198,9 @@ var sdk = require('postman-collection'),
         // at this point of time, we should have traversed all items mentioned in entrypoint and created a linear
         // subset of items. However, if post that, we still have items remaining in lookup object, that implies that
         // extra items were present in user input and corresponding items for those do not exist in collection. As such
-        // we need to bail out if any of the given entry-point is not found.
+        // we need to bail out with an error if any of the given entry-point is not found.
         if (Object.keys(entrypointLookup).length) {
-            return callback(null, []);
+            return callback(new Error('Unable to find an entry point'));
         }
 
         // extract runnable items from the searched items.

test/unit/extract-runnable-items.test.js

@@ -275,16 +275,18 @@ describe('extractRunnableItems', function () {
             );
         });
 
-        it('should bail out if any of the given entrypoint is not found. ', function (done) {
+        it('should throw an error if non-existent entry points were provided', function (done) {
             extractRunnableItems(
                 collection, {
-                    execute: ['ID3', 'RANDOM'],
-                    lookupStrategy: 'multipleIdOrName'
+                    execute: ['RANDOM', 'F1.R1', 'F2.R1'],
+                    lookupStrategy: 'multipleIdOrName',
+                    abortOnError: true
                 },
                 function (err, runnableItems, entrypoint) {
-                    expect(err).to.be.null;
-                    expect(runnableItems).to.eql([]);
+                    expect(err.message).to.equal('Unable to find an entry point');
+                    expect(runnableItems).to.be.undefined;
                     expect(entrypoint).to.be.undefined;
+
                     done();
                 }
             );