diff --git a/assets/js/__tests__/imagesclientside.spec.ts b/assets/js/__tests__/imagesclientside.spec.ts
new file mode 100644
index 00000000..3f3feb88
--- /dev/null
+++ b/assets/js/__tests__/imagesclientside.spec.ts
@@ -0,0 +1,161 @@
+import { filterNode, initImagesClientside } from '../imagesclientside';
+import { parseSearch } from '../match_query';
+import { matchNone } from '../query/boolean';
+import { assertNotNull } from '../utils/assert';
+import { $ } from '../utils/dom';
+
+describe('filterNode', () => {
+  beforeEach(() => {
+    window.booru.hiddenTagList = [];
+    window.booru.spoileredTagList = [];
+    window.booru.ignoredTagList = [];
+    window.booru.imagesWithDownvotingDisabled = [];
+
+    window.booru.hiddenFilter = matchNone();
+    window.booru.spoileredFilter = matchNone();
+  });
+
+  function makeMediaContainer() {
+    const element = document.createElement('div');
+    element.innerHTML = `
+      <div class="image-container" data-image-id="1" data-image-tags="[1]">
+        <div class="js-spoiler-info-overlay"></div>
+        <picture><img src=""/></picture>
+      </div>
+    `;
+    return [ element, assertNotNull($<HTMLDivElement>('.js-spoiler-info-overlay', element)) ];
+  }
+
+  it('should show image media boxes not matching any filter', () => {
+    const [ container, spoilerOverlay ] = makeMediaContainer();
+
+    filterNode(container);
+    expect(spoilerOverlay).not.toContainHTML('(Complex Filter)');
+    expect(spoilerOverlay).not.toContainHTML('(unknown tag)');
+    expect(window.booru.imagesWithDownvotingDisabled).not.toContain('1');
+  });
+
+  it('should spoiler media boxes spoilered by a tag filter', () => {
+    const [ container, spoilerOverlay ] = makeMediaContainer();
+    window.booru.spoileredTagList = [1];
+
+    filterNode(container);
+    expect(spoilerOverlay).toContainHTML('(unknown tag)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should spoiler media boxes spoilered by a complex filter', () => {
+    const [ container, spoilerOverlay ] = makeMediaContainer();
+    window.booru.spoileredFilter = parseSearch('id:1');
+
+    filterNode(container);
+    expect(spoilerOverlay).toContainHTML('(Complex Filter)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should hide media boxes hidden by a tag filter', () => {
+    const [ container, spoilerOverlay ] = makeMediaContainer();
+    window.booru.hiddenTagList = [1];
+
+    filterNode(container);
+    expect(spoilerOverlay).toContainHTML('[HIDDEN]');
+    expect(spoilerOverlay).toContainHTML('(unknown tag)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should hide media boxes hidden by a complex filter', () => {
+    const [ container, spoilerOverlay ] = makeMediaContainer();
+    window.booru.hiddenFilter = parseSearch('id:1');
+
+    filterNode(container);
+    expect(spoilerOverlay).toContainHTML('[HIDDEN]');
+    expect(spoilerOverlay).toContainHTML('(Complex Filter)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  function makeImageBlock(): HTMLElement[] {
+    const element = document.createElement('div');
+    element.innerHTML = `
+      <div class="image-show-container" data-image-id="1" data-image-tags="[1]">
+        <div class="image-filtered hidden">
+          <img src=""/>
+          <span class="filter-explanation"></span>
+        </div>
+        <div class="image-show hidden">
+          <picture><img src=""/></picture>
+        </div>
+      </div>
+    `;
+    return [
+      element,
+      assertNotNull($<HTMLDivElement>('.image-filtered', element)),
+      assertNotNull($<HTMLDivElement>('.image-show', element)),
+      assertNotNull($<HTMLSpanElement>('.filter-explanation', element))
+    ];
+  }
+
+  it('should show image blocks not matching any filter', () => {
+    const [ container, imageFiltered, imageShow ] = makeImageBlock();
+
+    filterNode(container);
+    expect(imageFiltered).toHaveClass('hidden');
+    expect(imageShow).not.toHaveClass('hidden');
+    expect(window.booru.imagesWithDownvotingDisabled).not.toContain('1');
+  });
+
+  it('should spoiler image blocks spoilered by a tag filter', () => {
+    const [ container, imageFiltered, imageShow, filterExplanation ] = makeImageBlock();
+    window.booru.spoileredTagList = [1];
+
+    filterNode(container);
+    expect(imageFiltered).not.toHaveClass('hidden');
+    expect(imageShow).toHaveClass('hidden');
+    expect(filterExplanation).toContainHTML('spoilered by');
+    expect(filterExplanation).toContainHTML('(unknown tag)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should spoiler image blocks spoilered by a complex filter', () => {
+    const [ container, imageFiltered, imageShow, filterExplanation ] = makeImageBlock();
+    window.booru.spoileredFilter = parseSearch('id:1');
+
+    filterNode(container);
+    expect(imageFiltered).not.toHaveClass('hidden');
+    expect(imageShow).toHaveClass('hidden');
+    expect(filterExplanation).toContainHTML('spoilered by');
+    expect(filterExplanation).toContainHTML('complex tag expression');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should hide image blocks hidden by a tag filter', () => {
+    const [ container, imageFiltered, imageShow, filterExplanation ] = makeImageBlock();
+    window.booru.hiddenTagList = [1];
+
+    filterNode(container);
+    expect(imageFiltered).not.toHaveClass('hidden');
+    expect(imageShow).toHaveClass('hidden');
+    expect(filterExplanation).toContainHTML('hidden by');
+    expect(filterExplanation).toContainHTML('(unknown tag)');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+  it('should hide image blocks hidden by a complex filter', () => {
+    const [ container, imageFiltered, imageShow, filterExplanation ] = makeImageBlock();
+    window.booru.hiddenFilter = parseSearch('id:1');
+
+    filterNode(container);
+    expect(imageFiltered).not.toHaveClass('hidden');
+    expect(imageShow).toHaveClass('hidden');
+    expect(filterExplanation).toContainHTML('hidden by');
+    expect(filterExplanation).toContainHTML('complex tag expression');
+    expect(window.booru.imagesWithDownvotingDisabled).toContain('1');
+  });
+
+});
+
+describe('initImagesClientside', () => {
+  it('should initialize the imagesWithDownvotingDisabled array', () => {
+    initImagesClientside();
+    expect(window.booru.imagesWithDownvotingDisabled).toEqual([]);
+  });
+});
diff --git a/assets/js/imagesclientside.ts b/assets/js/imagesclientside.ts
index 61e1d1ac..add108c9 100644
--- a/assets/js/imagesclientside.ts
+++ b/assets/js/imagesclientside.ts
@@ -2,6 +2,7 @@
  * Client-side image filtering/spoilering.
  */
 
+import { assertNotUndefined } from './utils/assert';
 import { $$, escapeHtml } from './utils/dom';
 import { setupInteractions } from './interactions';
 import { showThumb, showBlock, spoilerThumb, spoilerBlock, hideThumb } from './utils/image';
@@ -15,20 +16,20 @@ function run(
   img: HTMLDivElement,
   tags: TagData[],
   complex: AstMatcher,
-  callback: RunCallback,
+  runCallback: RunCallback
 ): boolean {
   const hit = (() => {
     // Check tags array first to provide more precise filter explanations
     const hitTags = imageHitsTags(img, tags);
     if (hitTags.length !== 0) {
-      callback(img, hitTags, 'tags');
+      runCallback(img, hitTags, 'tags');
       return true;
     }
 
     // No tags matched, try complex filter AST
     const hitComplex = imageHitsComplex(img, complex);
     if (hitComplex) {
-      callback(img, hitTags, 'complex');
+      runCallback(img, hitTags, 'complex');
       return true;
     }
 
@@ -36,9 +37,9 @@ function run(
     return false;
   })();
 
-  if (hit && img.dataset.imageId) {
+  if (hit) {
     // Disallow negative interaction on image which is not visible
-    window.booru.imagesWithDownvotingDisabled.push(img.dataset.imageId);
+    window.booru.imagesWithDownvotingDisabled.push(assertNotUndefined(img.dataset.imageId));
   }
 
   return hit;