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merged 2 commits into from
Oct 1, 2025
Merged

test: add unit tests for Swap source (closes #33) #38

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178c043
test(sources): add and refine Swap source unit tests; cover default r…
pradeepkaswan Oct 1, 2025
e6830e5
Merge branch 'master' into test/add-swap-source-tests
dariomannu Oct 1, 2025
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177 changes: 113 additions & 64 deletions src/sources/swap-source.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,27 +6,28 @@ import { Swap, swap } from './swap-source';

describe('Swap Event Adapter', () => {

it('Swaps a value in an element with a static string', () => {
const oldValue = 'old data';
const newValue = 'new data';
it('Swaps a value from an element with a static string', () => {
const oldValue = 'old data';
const newValue = 'new data';

const el = MockElement({
const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});
type: 'text',
value: oldValue,
});

const eventData = MockEvent('input', {
target: el as HTMLInputElement
});
const eventData = MockEvent('input', {
target: el as HTMLInputElement
});

const handlerSpy = jest.fn();
const source = Swap(newValue)(handlerSpy);
source.next(eventData);
const handlerSpy = jest.fn();
const source = Swap(newValue, handlerSpy);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual(newValue);
});
source.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual(newValue);
})

it('Swaps a value in an element using a function', () => {
const oldValue = 'old data';
Expand All @@ -44,7 +45,8 @@ describe('Swap Event Adapter', () => {
const replaceFn = (v: string) => v.toUpperCase();

const handlerSpy = jest.fn();
const source = Swap(replaceFn)(handlerSpy);
const source = Swap(undefined, handlerSpy);

source.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
Expand Down Expand Up @@ -76,51 +78,98 @@ describe('Swap Event Adapter', () => {

describe('swap Event Operator', () => {

it('Swaps and emits a value from an element with static string', () => {
const oldValue = 'old data';
const newValue = 'new data';

const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});

const eventData = MockEvent('input', {
target: el as HTMLInputElement
});

const handlerSpy = jest.fn();
const pipeline = new Subject<typeof eventData>().pipe(swap(newValue)) as Observable<string> & Subject<typeof eventData>;
pipeline.subscribe(x => handlerSpy(x));
pipeline.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual(newValue);
});

it('Swaps and emits a value from an element using function', () => {
const oldValue = 'old data';

const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});

const eventData = MockEvent('input', {
target: el as HTMLInputElement
});

const replaceFn = (v: string) => v.toUpperCase();

const handlerSpy = jest.fn();
const pipeline = new Subject<typeof eventData>().pipe(swap(replaceFn)) as Observable<string> & Subject<typeof eventData>;
pipeline.subscribe(x => handlerSpy(x));
pipeline.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual('OLD DATA');
});
it('Swaps and emits a value from an element with a static string', () => {
const oldValue = 'old data';
const newValue = 'new data';

const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});

const eventData = MockEvent('input', {
target: el as HTMLInputElement
});

const handlerSpy = jest.fn();
const pipeline = new Subject<typeof eventData>().pipe(swap(newValue)) as Observable<string> & Subject<typeof eventData>;

pipeline.subscribe(x => handlerSpy(x));
pipeline.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual(newValue);
});

it('Swaps and emits a value from an element with empty string', () => {
const oldValue = 'old data';

const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});

const eventData = MockEvent('input', {
target: el as HTMLInputElement
});
const handlerSpy = jest.fn();
const pipeline = new Subject<typeof eventData>().pipe(swap('')) as Observable<string> & Subject<typeof eventData>;

pipeline.subscribe(x => handlerSpy(x));
pipeline.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual('');
});



it('Swaps a value using a function that generates new value from old', () => {
const oldValue = 'test';
const replacementFn = (v: string) => `${v}_modified`;
const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: oldValue,
});
const eventData = MockEvent('input', {
target: el as HTMLInputElement
});
const handlerSpy = jest.fn();
const pipeline = new Subject<typeof eventData>().pipe(swap(replacementFn)) as Observable<string> & Subject<typeof eventData>;

pipeline.subscribe(x => handlerSpy(x));
pipeline.next(eventData);

expect(handlerSpy).toHaveBeenCalledWith(oldValue);
expect(el.value).toEqual('test_modified');
});

it('Handles multiple swap operations in sequence', () => {
const values = ['first', 'second', 'third'];
const el = MockElement({
tagName: 'INPUT',
type: 'text',
value: values[0],
});
const handlerSpy = jest.fn();
const pipeline = new Subject<Event>().pipe(swap('replacement')) as Observable<string> & Subject<Event>;

pipeline.subscribe(x => handlerSpy(x));

values.forEach(val => {
el.value = val;
const eventData = MockEvent('input', { target: el as HTMLInputElement });
pipeline.next(eventData);
});

expect(handlerSpy).toHaveBeenCalledTimes(3);
expect(handlerSpy).toHaveBeenNthCalledWith(1, 'first');
expect(handlerSpy).toHaveBeenNthCalledWith(2, 'second');
expect(handlerSpy).toHaveBeenNthCalledWith(3, 'third');
expect(el.value).toEqual('replacement');
});
});

});
17 changes: 9 additions & 8 deletions src/sources/swap-source.ts
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Expand Up @@ -7,10 +7,11 @@ import { curry } from '../utils/curry';
import { EventListenerFunction } from '../types/dom';

/**
* An Event Source Operator that "cuts" the value of the underlying <input> element
* and resets it to the provided value or empty otherwise
* @param handler A handler function or observer to send events to
* @returns EventSource<string>
* An Event Operator that swaps the value of the underlying <input> element
* with the provided replacement (or empty string by default) and emits the previous value.
* This operator mutates the element's value as a side effect.
* @param replacement A string or function used to compute the new value
* @returns OperatorFunction<Event, string>
*/
export const swap = <E extends Event>(replacement: string | Function) =>
map((e: E) => {
Expand All @@ -22,10 +23,10 @@ export const swap = <E extends Event>(replacement: string | Function) =>
;

/**
* An Event Source that "cuts" the value of the underlying &lt;input&gt; element
* and resets it to the provided value or empty otherwise
* @param replacement A new value to swap the current element's value with
* @param source A handler function or observer to send events to
* An Event Adapter that swaps the value of the underlying &lt;input&gt; element
* with the provided replacement (or empty string by default) and emits the previous value to the given target.
* @param replacement A new value or function to compute the element's next value
* @param source A handler function or observer to send emitted values to
* @returns EventSource<string>
*/
export const Swap =
Expand Down