test: add coverage for window scroll mode, initialScrollY, touch PTR, null scrollableTarget, and missing refreshFunction

Author: iamdarshshah

src/__tests__/bottom.test.tsx

@@ -73,4 +73,27 @@ describe('bottom detection triggers next', () => {
 
     expect(next).toHaveBeenCalledTimes(1);
   });
+
+  it('uses null root (viewport) in window scroll mode', () => {
+    const next = jest.fn();
+    render(
+      <InfiniteScroll
+        dataLength={0}
+        loader={'Loading...'}
+        hasMore={true}
+        next={next}
+      >
+        <div />
+      </InfiniteScroll>
+    );
+
+    // No height, no scrollableTarget → root must be null (viewport IO)
+    expect(MockIntersectionObserver.instances[0].options.root).toBeNull();
+
+    act(() => {
+      MockIntersectionObserver.instances[0].triggerIntersect();
+    });
+
+    expect(next).toHaveBeenCalled();
+  });
 });

src/__tests__/index.test.tsx

@@ -105,6 +105,88 @@ describe('React Infinite Scroll Component', () => {
     });
   });
 
+  describe('When pullDownToRefresh is true but refreshFunction is missing', () => {
+    it('throws an error', () => {
+      const consoleSpy = jest
+        .spyOn(console, 'error')
+        .mockImplementation(() => {});
+
+      expect(() =>
+        render(
+          <InfiniteScroll
+            dataLength={0}
+            loader={'Loading...'}
+            hasMore={false}
+            next={() => {}}
+            pullDownToRefresh
+          >
+            <div />
+          </InfiniteScroll>
+        )
+      ).toThrow('Mandatory prop "refreshFunction" missing');
+
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe('initialScrollY', () => {
+    it('calls scrollTo on mount when scrollHeight exceeds initialScrollY', () => {
+      const scrollToSpy = jest.fn();
+      const originalScrollTo = HTMLElement.prototype.scrollTo;
+      HTMLElement.prototype.scrollTo = scrollToSpy as any;
+
+      Object.defineProperty(HTMLElement.prototype, 'scrollHeight', {
+        configurable: true,
+        get: () => 500,
+      });
+
+      render(
+        <InfiniteScroll
+          dataLength={0}
+          loader={'Loading...'}
+          hasMore={false}
+          next={() => {}}
+          height={100}
+          initialScrollY={200}
+        >
+          <div />
+        </InfiniteScroll>
+      );
+
+      expect(scrollToSpy).toHaveBeenCalledWith(0, 200);
+
+      HTMLElement.prototype.scrollTo = originalScrollTo;
+      Object.defineProperty(HTMLElement.prototype, 'scrollHeight', {
+        configurable: true,
+        get: () => 0,
+      });
+    });
+
+    it('does not call scrollTo when scrollHeight is insufficient', () => {
+      const scrollToSpy = jest.fn();
+      const originalScrollTo = HTMLElement.prototype.scrollTo;
+      HTMLElement.prototype.scrollTo = scrollToSpy as any;
+
+      // scrollHeight defaults to 0 in jsdom — less than initialScrollY
+      render(
+        <InfiniteScroll
+          dataLength={0}
+          loader={'Loading...'}
+          hasMore={false}
+          next={() => {}}
+          height={100}
+          initialScrollY={200}
+        >
+          <div />
+        </InfiniteScroll>
+      );
+
+      expect(scrollToSpy).not.toHaveBeenCalled();
+
+      HTMLElement.prototype.scrollTo = originalScrollTo;
+    });
+  });
+
   describe('When user scrolls to the bottom', () => {
     it('does not show loader if hasMore is false', () => {
       const { queryByText } = render(

src/__tests__/pullDown.test.tsx

@@ -72,4 +72,48 @@ describe('pull down to refresh', () => {
 
     expect(refresh).toHaveBeenCalled();
   });
+
+  it('calls refreshFunction after touch pull past threshold', () => {
+    const refresh = jest.fn();
+    const { container } = render(
+      <InfiniteScroll
+        dataLength={10}
+        loader={'Loading...'}
+        hasMore={true}
+        next={() => {}}
+        height={200}
+        pullDownToRefresh
+        pullDownToRefreshThreshold={50}
+        refreshFunction={refresh}
+        pullDownToRefreshContent={<div style={{ height: 100 }}>Pull</div>}
+      >
+        <div />
+      </InfiniteScroll>
+    );
+
+    const node = container.querySelector(
+      '.infinite-scroll-component'
+    ) as HTMLElement;
+
+    const touchStart = new TouchEvent('touchstart', { bubbles: true });
+    Object.defineProperty(touchStart, 'touches', { value: [{ pageY: 0 }] });
+    act(() => {
+      node.dispatchEvent(touchStart);
+    });
+
+    const touchMove = new TouchEvent('touchmove', { bubbles: true });
+    Object.defineProperty(touchMove, 'touches', { value: [{ pageY: 60 }] });
+    act(() => {
+      node.dispatchEvent(touchMove);
+    });
+
+    expect(node.style.transform).toBe('translate3d(0px, 60px, 0px)');
+
+    const touchEnd = new TouchEvent('touchend', { bubbles: true });
+    act(() => {
+      node.dispatchEvent(touchEnd);
+    });
+
+    expect(refresh).toHaveBeenCalled();
+  });
 });

src/__tests__/scrollableTarget.test.tsx

@@ -66,4 +66,25 @@ describe('scrollableTarget as element id', () => {
 
     document.body.removeChild(target);
   });
+
+  it('warns when scrollableTarget is null', () => {
+    const warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+    render(
+      <InfiniteScroll
+        dataLength={0}
+        loader={'Loading...'}
+        hasMore={true}
+        next={() => {}}
+        scrollableTarget={null}
+      >
+        <div />
+      </InfiniteScroll>
+    );
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('scrollableTarget but it is null')
+    );
+    warnSpy.mockRestore();
+  });
 });