diff --git a/src/test/ContactBulkActions.test.ts b/src/test/ContactBulkActions.test.ts
index 46abb51a..b7da4072 100644
--- a/src/test/ContactBulkActions.test.ts
+++ b/src/test/ContactBulkActions.test.ts
@@ -493,13 +493,65 @@ describe('ContactBulkActions', () => {
       wrapper = mountComponent()
       const html = wrapper.html()
       
-      // Basic structure validation
-      expect(html).toContain('<div')
-      expect(html).toContain('class="mt-2 w-full text-left"')
+      // Validate specific structure with regex patterns
+      expect(html).toMatch(/<div[^>]*class="[^"]*mt-2[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*w-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*text-left[^"]*"[^>]*>/)
+      expect(html).toMatch(/<input[^>]*type="checkbox"[^>]*>/)
+      expect(html).toMatch(/<button[^>]*class="[^"]*[^"]*"[^>]*>/)
+      
+      // Validate accessibility attributes
       expect(html).toContain('data-testid="contactCheckAllBottom"')
       expect(html).toContain('Copy')
     })
 
+    it('should maintain consistent structure with different prop combinations', () => {
+      const testCases = [
+        { showGiveNumbers: false, allContactsSelected: true, copyButtonClass: 'btn-primary', copyButtonDisabled: false },
+        { showGiveNumbers: false, allContactsSelected: false, copyButtonClass: 'btn-secondary', copyButtonDisabled: true },
+        { showGiveNumbers: true, allContactsSelected: false, copyButtonClass: 'btn-primary', copyButtonDisabled: false }
+      ]
+      
+      testCases.forEach(props => {
+        const testWrapper = mountComponent(props)
+        const html = testWrapper.html()
+        
+        if (!props.showGiveNumbers) {
+          // Should render checkbox and button
+          expect(html).toMatch(/<input[^>]*type="checkbox"[^>]*>/)
+          expect(html).toMatch(/<button[^>]*class="[^"]*[^"]*"[^>]*>/)
+          expect(html).toContain('Copy')
+          expect(html).toContain('data-testid="contactCheckAllBottom"')
+        } else {
+          // Should render outer div but inner elements are conditionally rendered
+          expect(html).toMatch(/<div[^>]*class="[^"]*mt-2[^"]*"[^>]*>/)
+          expect(html).not.toContain('<input')
+          expect(html).not.toContain('<button')
+          expect(html).not.toContain('Copy')
+        }
+      })
+    })
+
+    it('should maintain accessibility attributes consistently', () => {
+      wrapper = mountComponent()
+      const html = wrapper.html()
+      
+      // Validate accessibility attributes
+      expect(html).toContain('data-testid="contactCheckAllBottom"')
+      
+      // Validate semantic structure
+      expect(html).toMatch(/<div[^>]*class="[^"]*mt-2[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*w-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*text-left[^"]*"[^>]*>/)
+      
+      // Validate form controls
+      const checkbox = wrapper.find('input[type="checkbox"]')
+      const button = wrapper.find('button')
+      expect(checkbox.exists()).toBe(true)
+      expect(button.exists()).toBe(true)
+      expect(checkbox.attributes('data-testid')).toBe('contactCheckAllBottom')
+    })
+
     it('should have consistent CSS classes', () => {
       wrapper = mountComponent()
       const container = wrapper.find('.mt-2')
diff --git a/src/test/LargeIdenticonModal.test.ts b/src/test/LargeIdenticonModal.test.ts
index 0486d437..fed7b807 100644
--- a/src/test/LargeIdenticonModal.test.ts
+++ b/src/test/LargeIdenticonModal.test.ts
@@ -746,11 +746,57 @@ describe('LargeIdenticonModal', () => {
       wrapper = mountComponent()
       const html = wrapper.html()
       
-      // Basic structure validation
-      expect(html).toContain('<div')
-      expect(html).toContain('class="fixed z-[100] top-0 inset-x-0 w-full"')
-      expect(html).toContain('class="absolute inset-0 h-screen flex flex-col items-center justify-center bg-slate-900/50"')
+      // Validate specific structure with regex patterns
+      expect(html).toMatch(/<div[^>]*class="[^"]*fixed[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*z-\[100\][^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*absolute[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*bg-slate-900\/50[^"]*"[^>]*>/)
+      
+      // Validate EntityIcon component
       expect(html).toContain('EntityIcon')
+      expect(html).toContain('entity-icon-stub')
+      
+      // Note: Component doesn't have role="dialog" or aria-modal attributes
+      // These are not present in the actual component template
+    })
+
+    it('should maintain consistent structure with different contact states', () => {
+      const testCases = [
+        { contact: mockContact },
+        { contact: createSimpleMockContact({ name: 'Test Contact' }) },
+        { contact: createSimpleMockContact({ id: 'complex-123', name: 'Complex Contact' }) }
+      ]
+      
+      testCases.forEach(props => {
+        const testWrapper = mountComponent(props)
+        const html = testWrapper.html()
+        
+        // Core modal structure should always be present
+        expect(html).toMatch(/<div[^>]*class="[^"]*fixed[^"]*"[^>]*>/)
+        expect(html).toMatch(/<div[^>]*class="[^"]*absolute[^"]*"[^>]*>/)
+        
+        // EntityIcon should always be present when contact exists
+        expect(html).toContain('EntityIcon')
+        expect(html).toContain('entity-icon-stub')
+      })
+    })
+
+    it('should maintain accessibility attributes consistently', () => {
+      wrapper = mountComponent()
+      const html = wrapper.html()
+      
+      // Note: Component doesn't have ARIA attributes in template
+      // These would need to be added to the component for accessibility
+      
+      // Validate semantic structure
+      expect(html).toMatch(/<div[^>]*class="[^"]*fixed[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*absolute[^"]*"[^>]*>/)
+      
+      // Validate modal positioning
+      const modal = wrapper.find('.fixed')
+      expect(modal.exists()).toBe(true)
+      expect(modal.classes()).toContain('z-[100]')
+      expect(modal.classes()).toContain('top-0')
     })
 
     it('should have consistent CSS classes', () => {
diff --git a/src/test/ProjectIcon.test.ts b/src/test/ProjectIcon.test.ts
index 1cfbf265..392d26b8 100644
--- a/src/test/ProjectIcon.test.ts
+++ b/src/test/ProjectIcon.test.ts
@@ -432,9 +432,54 @@ describe('ProjectIcon', () => {
       wrapper = mountComponent()
       const html = wrapper.html()
       
-      // Basic structure validation
-      expect(html).toContain('<div')
-      expect(html).toContain('class="h-full w-full object-contain"')
+      // Validate specific structure with regex patterns
+      expect(html).toMatch(/<div[^>]*class="[^"]*h-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*w-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*object-contain[^"]*"[^>]*>/)
+      
+      // Validate SVG structure when no imageUrl
+      expect(html).toContain('<svg')
+      expect(html).toContain('xmlns="http://www.w3.org/2000/svg"')
+    })
+
+    it('should maintain consistent structure with different prop combinations', () => {
+      const testCases = [
+        { entityId: 'test', iconSize: 64, imageUrl: '', linkToFullImage: false },
+        { entityId: 'test', iconSize: 64, imageUrl: 'https://example.com/image.jpg', linkToFullImage: true },
+        { entityId: '', iconSize: 64, imageUrl: '', linkToFullImage: false }
+      ]
+      
+      testCases.forEach(props => {
+        const testWrapper = mountComponent(props)
+        const html = testWrapper.html()
+        
+        // Core structure should always be present
+        expect(html).toMatch(/<div[^>]*class="[^"]*h-full[^"]*"[^>]*>/)
+        
+        if (props.imageUrl && props.linkToFullImage) {
+          // Should render as link with image
+          expect(html).toMatch(/<a[^>]*href="[^"]*"[^>]*>/)
+          expect(html).toMatch(/<img[^>]*src="[^"]*"[^>]*>/)
+        } else if (props.imageUrl) {
+          // Should render image without link
+          expect(html).toMatch(/<img[^>]*src="[^"]*"[^>]*>/)
+        } else {
+          // Should render SVG
+          expect(html).toContain('<svg')
+        }
+      })
+    })
+
+    it('should maintain accessibility structure consistently', () => {
+      wrapper = mountComponent()
+      const html = wrapper.html()
+      
+      // Validate semantic structure
+      expect(html).toMatch(/<div[^>]*class="[^"]*h-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*w-full[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*object-contain[^"]*"[^>]*>/)
+      
+      // Validate SVG accessibility
       expect(html).toContain('<svg')
       expect(html).toContain('xmlns="http://www.w3.org/2000/svg"')
     })
diff --git a/src/test/README.md b/src/test/README.md
index 7b920ec2..ef365ccc 100644
--- a/src/test/README.md
+++ b/src/test/README.md
@@ -21,6 +21,7 @@ This directory contains comprehensive unit tests for TimeSafari components using
 *EntityIcon.vue has 100% coverage but no dedicated test file (covered by LargeIdenticonModal tests)
 
 ### 📊 **Coverage Metrics**
+
 - **Total Tests**: 149 tests passing
 - **Test Files**: 5 files
 - **Components Covered**: 5 simple components
@@ -32,6 +33,7 @@ This directory contains comprehensive unit tests for TimeSafari components using
 ## Testing Infrastructure
 
 ### **Core Technologies**
+
 - **Vitest**: Fast unit testing framework
 - **JSDOM**: Browser-like environment for Node.js
 - **@vue/test-utils**: Vue component testing utilities
@@ -151,6 +153,103 @@ it('should have correct CSS classes', () => {
 - Accessibility attribute consistency
 - Visual structure verification
 
+## Testing Philosophy
+
+### **Defensive Programming Validation**
+
+The primary purpose of our comprehensive error handling tests is to **prevent component and system failures** in real-world scenarios. Our testing philosophy focuses on:
+
+#### **1. Real-World Edge Case Protection**
+- **Invalid API responses**: Test components when backend returns `null` instead of expected objects
+- **Network failures**: Verify graceful handling of missing or corrupted data
+- **User input errors**: Test with malformed data, special characters, and extreme values
+- **Concurrent operations**: Ensure stability during rapid state changes and simultaneous interactions
+
+#### **2. System Stability Assurance**
+- **Cascading failures**: Prevent one component's error from breaking the entire application
+- **Memory leaks**: Ensure components clean up properly even when errors occur
+- **Performance degradation**: Verify components remain responsive under error conditions
+
+#### **3. Production Readiness**
+- **User Experience Protection**: Users don't see blank screens or error messages
+- **Developer Confidence**: Safe refactoring without fear of breaking edge cases
+- **System Reliability**: Prevents one bad API response from crashing the entire app
+
+### **Comprehensive Error Scenarios**
+
+Our error handling tests cover:
+
+#### **RegistrationNotice Component Protection**
+- Prevents crashes when `isRegistered` or `show` props are malformed
+- Ensures the "Share Your Info" button still works even with invalid data
+- Protects against rapid prop changes causing UI inconsistencies
+
+#### **LargeIdenticonModal Component Protection**
+- Prevents modal rendering with invalid contact data that could break the UI
+- Ensures the close functionality works even with malformed contact objects
+- Protects against EntityIcon component failures cascading to the modal
+
+### **Error Testing Categories**
+
+#### **Invalid Input Testing**
+```typescript
+// Test 10+ different invalid prop combinations
+const invalidPropCombinations = [
+  null, undefined, 'invalid', 0, -1, {}, [], 
+  () => {}, NaN, Infinity
+]
+```
+
+#### **Malformed Data Testing**
+```typescript
+// Test various malformed data structures
+const malformedData = [
+  { id: 'invalid' }, { name: null }, 
+  { id: 0, name: '' }, { id: NaN, name: NaN }
+]
+```
+
+#### **Extreme Value Testing**
+```typescript
+// Test boundary conditions and extreme values
+const extremeValues = [
+  Number.MAX_SAFE_INTEGER, Number.MIN_SAFE_INTEGER,
+  Infinity, NaN, '', '\t\n\r'
+]
+```
+
+#### **Concurrent Error Testing**
+```typescript
+// Test rapid changes with invalid data
+for (let i = 0; i < 50; i++) {
+  await wrapper.setProps({ 
+    contact: i % 2 === 0 ? null : malformedContact 
+  })
+}
+```
+
+### **Benefits Beyond Coverage**
+
+#### **1. Defensive Programming Validation**
+- Components handle unexpected data gracefully
+- No crashes or blank screens for users
+- Proper error boundaries and fallbacks
+
+#### **2. Real-World Resilience**
+- Tested against actual failure scenarios
+- Validated with realistic error conditions
+- Proven stability under adverse conditions
+
+#### **3. Developer Confidence**
+- Safe to refactor and extend components
+- Clear understanding of component behavior under stress
+- Reduced debugging time for edge cases
+
+#### **4. Production Stability**
+- Reduced support tickets and user complaints
+- Improved application reliability
+- Better user experience under error conditions
+
 ## Mock Implementation
 
 ### **Mock Component Structure**
diff --git a/src/test/RegistrationNotice.test.ts b/src/test/RegistrationNotice.test.ts
index 11309c91..657b2766 100644
--- a/src/test/RegistrationNotice.test.ts
+++ b/src/test/RegistrationNotice.test.ts
@@ -1118,13 +1118,69 @@ describe('RegistrationNotice', () => {
       wrapper = mountComponent()
       const html = wrapper.html()
       
-      // Basic structure validation
-      expect(html).toContain('<div')
-      expect(html).toContain('id="noticeBeforeAnnounce"')
+      // Validate specific structure with regex patterns
+      expect(html).toMatch(/<div[^>]*id="noticeBeforeAnnounce"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*bg-amber-200[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*text-amber-900[^"]*"[^>]*>/)
+      
+      // Validate button structure (actual classes from component)
+      expect(html).toMatch(/<button[^>]*class="[^"]*bg-gradient-to-b[^"]*"[^>]*>/)
+      expect(html).toMatch(/<button[^>]*class="[^"]*from-blue-400[^"]*"[^>]*>/)
+      expect(html).toMatch(/<button[^>]*class="[^"]*to-blue-700[^"]*"[^>]*>/)
+      expect(html).toMatch(/<button[^>]*class="[^"]*text-white[^"]*"[^>]*>/)
+      expect(html).toContain('Share Your Info')
+      
+      // Validate accessibility structure
       expect(html).toContain('role="alert"')
       expect(html).toContain('aria-live="polite"')
-      expect(html).toContain('<button')
-      expect(html).toContain('Share Your Info')
+      
+      // Validate responsive design classes
+      expect(html).toMatch(/class="[^"]*px-4[^"]*"/)
+      expect(html).toMatch(/class="[^"]*py-3[^"]*"/)
+      expect(html).toMatch(/class="[^"]*rounded-md[^"]*"/)
+    })
+
+    it('should maintain consistent structure with different prop combinations', () => {
+      const testCases = [
+        { isRegistered: true, show: true },
+        { isRegistered: false, show: true },
+        { isRegistered: true, show: false },
+        { isRegistered: false, show: false }
+      ]
+      
+      testCases.forEach(props => {
+        const testWrapper = mountComponent(props)
+        const html = testWrapper.html()
+        
+        // Component only renders when !isRegistered && show
+        if (!props.isRegistered && props.show) {
+          // Core structure should be present
+          expect(html).toMatch(/<div[^>]*id="noticeBeforeAnnounce"[^>]*>/)
+          expect(html).toMatch(/<button[^>]*class="[^"]*bg-gradient-to-b[^"]*"[^>]*>/)
+          expect(html).toContain('Share Your Info')
+        } else {
+          // Component should not render (v-if="!isRegistered && show")
+          expect(html).toBe('<!--v-if-->')
+        }
+      })
+    })
+
+    it('should maintain accessibility attributes consistently', () => {
+      wrapper = mountComponent()
+      const html = wrapper.html()
+      
+      // Validate ARIA attributes
+      expect(html).toContain('role="alert"')
+      expect(html).toContain('aria-live="polite"')
+      
+      // Validate semantic structure
+      expect(html).toMatch(/<div[^>]*class="[^"]*bg-amber-200[^"]*"[^>]*>/)
+      expect(html).toMatch(/<div[^>]*class="[^"]*text-amber-900[^"]*"[^>]*>/)
+      
+      // Validate button accessibility (button doesn't have type attribute in component)
+      const button = wrapper.find('button')
+      expect(button.exists()).toBe(true)
+      // Note: Component doesn't specify type="button", so we don't test for it
     })
 
     it('should have consistent CSS classes', () => {