test(ShareButtons-theme-contrast): verify Dark and Light Prefers-Color-Scheme Visual Cohesion (JhaSourav07#3298)

## Description

Fixes JhaSourav07#2765 

This PR introduces integration tests for `components/ShareButtons.tsx`
focusing on **Dark and Light Prefers-Color-Scheme Visual Cohesion**.
Since this component inherits dynamic colors from its parents via SVG
`currentColor`, these tests assert that the structural wrappers remain
completely transparent (`bg-transparent`) without forcing localized
colors that would disrupt the global dark/light modes.

## Pillar

- [ ] 🎨 Pillar 1 — New Theme Design
- [ ] 📐 Pillar 2 — Geometric SVG Improvement
- [ ] 🕐 Pillar 3 — Timezone Logic Optimization
- [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview
*(N/A - Integration Tests)*

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally (`vitest`).
- [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
- [x] My commits follow the Conventional Commits format (e.g.,
`feat(themes): ...`, `fix(calculate): ...`).
- [x] I have updated `README.md` if I added a new theme or URL
parameter.
- [x] I have started the repo.
- [x] I have made sure that i have only one commit to merge in this PR.
- [x] The SVG output matches the CommitPulse "premium quality" aesthetic
standard (no raw elements, smooth animations, correct fonts).
- [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions.

Author: JhaSourav07

components/ShareButtons.theme-contrast.test.tsx

@@ -0,0 +1,81 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { render, cleanup } from '@testing-library/react';
+import React from 'react';
+import ShareButtons from './ShareButtons';
+
+describe('ShareButtons - Theme Contrast & Visual Cohesion (Issue #2765 Equivalent)', () => {
+  beforeEach(() => {
+    cleanup();
+  });
+
+  it('Dual Theme Environment Mock (Dark/Light Presets Equivalent): inherently adapts to a light parent container', () => {
+    // Render inside a explicitly light container
+    const { container } = render(
+      <div
+        className="bg-white text-black dark:bg-black dark:text-white"
+        style={{ color: 'rgb(0, 0, 0)' }}
+      >
+        <ShareButtons url="https://example.com" />
+      </div>
+    );
+
+    // SVGs should inherit the parent color via currentColor, not force their own
+    const svgs = container.querySelectorAll('svg');
+    expect(svgs.length).toBe(2);
+
+    // We verify the SVG elements don't contain hardcoded fill colors that override inheritance
+    svgs.forEach((svg) => {
+      expect(['currentColor', null]).toContain(svg.getAttribute('fill')); // React icons use currentColor or inherit
+    });
+  });
+
+  it('Color Styling Adaptation (Visual Elements Equivalent): explicitly avoids hardcoded text color utilities', () => {
+    const { container } = render(<ShareButtons url="https://example.com" />);
+
+    const rootDiv = container.firstChild as HTMLElement;
+    const classes = rootDiv.className;
+
+    // Component should NOT force a color
+    expect(classes).not.toContain('text-white');
+    expect(classes).not.toContain('text-black');
+    expect(classes).not.toContain('text-'); // No text colors at all
+  });
+
+  it('Contrast Ratio Standards (Textual Elements Equivalent): avoids inline styles that could break contrast inheritance', () => {
+    const { container } = render(<ShareButtons url="https://example.com" />);
+
+    const anchors = container.querySelectorAll('a');
+
+    // Anchors must rely entirely on CSS cascades for contrast, no inline overrides
+    anchors.forEach((a) => {
+      expect(a.getAttribute('style')).toBeNull();
+    });
+  });
+
+  it('Custom Stylesheet Properties (Markup Classes Equivalent): relies solely on structural flex utilities for layout', () => {
+    const { container } = render(<ShareButtons url="https://example.com" />);
+
+    const rootDiv = container.firstChild as HTMLElement;
+
+    // Should be a structural flex container
+    expect(rootDiv.className).toContain('flex');
+    expect(rootDiv.className).toContain('gap-3');
+
+    // Should NOT have any custom theme hacks
+    expect(rootDiv.className).not.toContain('dark:');
+  });
+
+  it('Background Overlay Clipping (Foreground Colors Equivalent): remains completely transparent to avoid overlay clipping', () => {
+    const { container } = render(<ShareButtons url="https://example.com" />);
+
+    const rootDiv = container.firstChild as HTMLElement;
+
+    // Must not have any background colors that would clip against parent thematic overlays
+    expect(rootDiv.className).not.toContain('bg-');
+
+    const anchors = container.querySelectorAll('a');
+    anchors.forEach((a) => {
+      expect(a.className).not.toContain('bg-');
+    });
+  });
+});