test(domain): add TokenHasher tests RED

tests/SIGCM2.Application.Tests/Domain/TokenHasherTests.cs

@@ -0,0 +1,50 @@
+using SIGCM2.Domain.Security;
+
+namespace SIGCM2.Application.Tests.Domain;
+
+public class TokenHasherTests
+{
+    [Fact]
+    public void Sha256Base64Url_IsDeterministic()
+    {
+        const string raw = "my_test_raw_token_value_abc123";
+
+        var hash1 = TokenHasher.Sha256Base64Url(raw);
+        var hash2 = TokenHasher.Sha256Base64Url(raw);
+
+        Assert.Equal(hash1, hash2);
+        Assert.False(string.IsNullOrWhiteSpace(hash1));
+    }
+
+    [Fact]
+    public void Sha256Base64Url_ProducesUrlSafeString()
+    {
+        // Use many values to increase chance of hitting + / = in base64
+        for (var i = 0; i < 50; i++)
+        {
+            var raw = $"token_value_{i}_padding_test_xyz";
+            var hash = TokenHasher.Sha256Base64Url(raw);
+
+            Assert.DoesNotContain('+', hash);
+            Assert.DoesNotContain('/', hash);
+            Assert.DoesNotContain('=', hash);
+        }
+    }
+
+    [Fact]
+    public void Sha256Base64Url_DifferentInputsDifferentOutputs()
+    {
+        var hash1 = TokenHasher.Sha256Base64Url("token_a");
+        var hash2 = TokenHasher.Sha256Base64Url("token_b");
+
+        Assert.NotEqual(hash1, hash2);
+    }
+
+    [Fact]
+    public void Sha256Base64Url_ProducesExpectedLength()
+    {
+        // SHA-256 = 32 bytes. Base64url without padding: ceil(32 * 4/3) = 43 chars
+        var hash = TokenHasher.Sha256Base64Url("any_token_value");
+        Assert.Equal(43, hash.Length);
+    }
+}