diff --git a/tests/crypto-adapter.test.ts b/tests/crypto-adapter.test.ts
index de85b7b..83d9e3f 100644
--- a/tests/crypto-adapter.test.ts
+++ b/tests/crypto-adapter.test.ts
@@ -2,6 +2,48 @@ import { getCryptoRandomValues } from '../src/utils/crypto-adapter';
 
 describe('crypto-adapter', () => {
 	describe('getCryptoRandomValues', () => {
+		it('should use window.crypto in browser environment', () => {
+			// Save reference to global
+			const globalRef = global as any;
+			const originalWindow = globalRef.window;
+
+			try {
+				// Mock browser environment with window.crypto
+				const mockGetRandomValues = jest.fn((array: any) => {
+					// Fill with mock random values
+					for (let i = 0; i < array.length; i++) {
+						array[i] = Math.floor(Math.random() * 256);
+					}
+					return array;
+				});
+
+				globalRef.window = {
+					crypto: {
+						getRandomValues: mockGetRandomValues
+					}
+				};
+
+				// Clear module cache to force re-evaluation
+				jest.resetModules();
+
+				// Re-import the function
+				const { getCryptoRandomValues: reloadedGetCryptoRandomValues } = require('../src/utils/crypto-adapter');
+
+				// Should use window.crypto
+				const array = new Uint8Array(32);
+				const result = reloadedGetCryptoRandomValues(array);
+
+				expect(result).toBe(array);
+				expect(mockGetRandomValues).toHaveBeenCalledWith(array);
+			} finally {
+				// Restore original window
+				globalRef.window = originalWindow;
+
+				// Clear module cache again to restore normal state
+				jest.resetModules();
+			}
+		});
+
 		it('should fill Uint8Array with random values', () => {
 			const array = new Uint8Array(32);
 			const result = getCryptoRandomValues(array);
@@ -52,5 +94,73 @@ describe('crypto-adapter', () => {
 			expect(medium.every(val => val >= 0 && val <= 255)).toBe(true);
 			expect(large.every(val => val >= 0 && val <= 255)).toBe(true);
 		});
+
+		it('should use Node.js crypto.webcrypto when window.crypto is not available', () => {
+			// Save references to global object and original values
+			const globalRef = global as any;
+			const originalWindow = globalRef.window;
+			const originalCrypto = originalWindow?.crypto;
+
+			try {
+				// Mock window without crypto to force Node.js crypto path
+				globalRef.window = { ...originalWindow };
+				delete globalRef.window.crypto;
+
+				// Clear module cache to force re-evaluation
+				jest.resetModules();
+
+				// Re-import the function
+				const { getCryptoRandomValues: reloadedGetCryptoRandomValues } = require('../src/utils/crypto-adapter');
+
+				// Should work using Node.js crypto.webcrypto
+				const array = new Uint8Array(32);
+				const result = reloadedGetCryptoRandomValues(array);
+
+				expect(result).toBe(array);
+				expect(result.length).toBe(32);
+				// Verify not all zeros
+				const hasNonZero = Array.from(result).some(val => val !== 0);
+				expect(hasNonZero).toBe(true);
+			} finally {
+				// Restore original values
+				globalRef.window = originalWindow;
+				if (originalWindow && originalCrypto) {
+					originalWindow.crypto = originalCrypto;
+				}
+
+				// Clear module cache again to restore normal state
+				jest.resetModules();
+			}
+		});
+
+		it('should throw error when no crypto API is available', () => {
+			// Save references to global object and original values
+			const globalRef = global as any;
+			const originalWindow = globalRef.window;
+			const originalGlobal = globalRef.global;
+
+			try {
+				// Remove window.crypto and global access
+				delete globalRef.window;
+				delete globalRef.global;
+
+				// Clear module cache to force re-evaluation
+				jest.resetModules();
+
+				// Re-import the function
+				const { getCryptoRandomValues: reloadedGetCryptoRandomValues } = require('../src/utils/crypto-adapter');
+
+				// Verify error is thrown
+				const array = new Uint8Array(32);
+				expect(() => reloadedGetCryptoRandomValues(array)).toThrow('No Web Crypto API available in this environment');
+			} finally {
+				// Restore original values
+				globalRef.window = originalWindow;
+				globalRef.global = originalGlobal;
+
+				// Clear module cache again to restore normal state
+				jest.resetModules();
+			}
+		});
 	});
 });