Add tests for custom merge options and callback

tests/browser/packages/support/arrays/merge.test.js

@@ -1,4 +1,8 @@
-import { ArrayMergeError, merge } from "@aedart/support/arrays";
+import {
+    ArrayMergeError,
+    merge,
+    Merger
+} from "@aedart/support/arrays";
 
 describe('@aedart/support/arrays', () => {
     describe('merge()', () => {
@@ -60,5 +64,56 @@ describe('@aedart/support/arrays', () => {
             expect(callback)
                 .toThrowError(ArrayMergeError);
         });
+
+        it('returns merger object when no args given', () => {
+            const merger = merge();
+
+            expect(merger)
+                .toBeInstanceOf(Merger);
+        });
+
+        it('can transfer functions', () => {
+
+            const fnA = () => false;
+            const fnB = () => true;
+
+            const a = [ fnA ];
+            const b = [ fnB ];
+
+            // --------------------------------------------------------------- //
+
+            const result = merge()
+                .using({ transferFunctions: true })
+                .of(a, b);
+
+            expect(result.length)
+                .withContext('Incorrect amount of elements in output')
+                .toBe(2);
+
+            expect(result[0])
+                .withContext('Function A not transferred')
+                .toBe(fnA);
+
+            expect(result[1])
+                .withContext('Function B not transferred')
+                .toBe(fnB);
+        });
+
+        it('can apply custom merge callback', () => {
+
+            const a = [ 1, 2, 3 ];
+            const b = [ 4, 5, 6 ];
+
+            // --------------------------------------------------------------- //
+
+            const result = merge()
+                .using((element) => {
+                    return element * 2;
+                })
+                .of(a, b);
+
+            expect(result)
+                .toEqual([ 2, 4, 6, 8, 10, 12 ]);
+        });
     }); 
 });