Added test for extract image function

Author: kommendorkapten

pkg/image/digest_test.go

@@ -0,0 +1,78 @@
+package image
+
+import (
+	"testing"
+)
+
+func TestExtractDigest(t *testing.T) {
+	tests := []struct {
+		name     string
+		imageID  string
+		expected string
+	}{
+		{
+			name:     "empty string",
+			imageID:  "",
+			expected: "",
+		},
+		{
+			name:     "docker-pullable format",
+			imageID:  "docker-pullable://nginx@sha256:abc123def456",
+			expected: "sha256:abc123def456",
+		},
+		{
+			name:     "docker format",
+			imageID:  "docker://sha256:abc123def456789",
+			expected: "sha256:abc123def456789",
+		},
+		{
+			name:     "just sha256 digest",
+			imageID:  "sha256:0123456789abcdef",
+			expected: "sha256:0123456789abcdef",
+		},
+		{
+			name:     "full gcr image with digest",
+			imageID:  "docker-pullable://gcr.io/my-project/my-image@sha256:fedcba9876543210",
+			expected: "sha256:fedcba9876543210",
+		},
+		{
+			name:     "registry with port and digest",
+			imageID:  "docker-pullable://localhost:5000/myapp@sha256:1234567890abcdef",
+			expected: "sha256:1234567890abcdef",
+		},
+		{
+			name:     "no sha256 prefix returns original",
+			imageID:  "some-random-id-without-sha",
+			expected: "some-random-id-without-sha",
+		},
+		{
+			name:     "digest with trailing space",
+			imageID:  "docker://sha256:abc123 extra",
+			expected: "sha256:abc123",
+		},
+		{
+			name:     "digest with trailing @",
+			imageID:  "sha256:abc123@extra",
+			expected: "sha256:abc123",
+		},
+		{
+			name:     "real world kubernetes imageID",
+			imageID:  "docker-pullable://ghcr.io/github/deployment-tracker@sha256:a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2",
+			expected: "sha256:a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2",
+		},
+		{
+			name:     "containerd format",
+			imageID:  "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+			expected: "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := ExtractDigest(tt.imageID)
+			if result != tt.expected {
+				t.Errorf("ExtractDigest(%q) = %q, want %q", tt.imageID, result, tt.expected)
+			}
+		})
+	}
+}