test: improve create_out_transition tests

test/transitions/index.ts

@@ -5,43 +5,62 @@ import { TransitionConfig } from 'svelte/transition';
 declare const global: any;
 
 describe('transitions', () => {
-  let originalRequestAnimationFrame: () => void;
+	let originalRequestAnimationFrame: () => void;
 
-  before(() => {
-    originalRequestAnimationFrame = global.requestAnimationFrame;
-    global.requestAnimationFrame = cb => cb();
-  });
+	before(() => {
+		originalRequestAnimationFrame = global.requestAnimationFrame;
+		global.requestAnimationFrame = (cb) => cb();
+	});
+
+	after(() => {
+		global.requestAnimationFrame = originalRequestAnimationFrame;
+	});
 
-  after(() => {
-    global.requestAnimationFrame = originalRequestAnimationFrame;
-  });
+	beforeEach(() => {
+		group_outros();
+	});
 
-  beforeEach(() => {
-    group_outros();
-  });
-  
 	describe('create_out_transition', () => {
-		describe('when then transition function returns undefined', () => {
+		describe('when then transition function does not return a tick function', () => {
 			describe('when calling the end function with reset param equals to true', () => {
 				it('should not throw an exception', () => {
+					const noTickConfigs: TransitionConfig[] = [undefined, null, {}];
+
+					noTickConfigs.forEach((config) => {
+						const node = document.createElement('div');
+						const { end } = create_out_transition(node, () => config, {});
+						let error: Error | null = null;
+
+						try {
+							end(true);
+						} catch (e) {
+							error = e;
+						}
+
+						assert.equal(error, null);
+					});
+				});
+			});
+		});
+
+		describe('when the transition function returns a config object with defined tick function', () => {
+			describe('when calling the end function with reset param equals to true', () => {
+				it('should call the tick function', () => {
 					const node = document.createElement('div');
+					let tick = 0;
 					const transitionConfig: TransitionConfig = {
-						duration: 0
+						duration: 0,
+						tick: () => (tick += 1)
 					};
 					const { end } = create_out_transition(
 						node,
-						() => undefined,
-						transitionConfig
+						() => transitionConfig,
+						{}
 					);
-					let error: Error | null = null;
 
-					try {
-						end(true);
-					} catch (e) {
-						error = e;
-					}
+					end(true);
 
-					assert.equal(error, null);
+					assert.equal(tick, 1);
 				});
 			});
 		});