@@ -0,0 +1,87 @@
+package optlink
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/yuin/goldmark"
+)
+
+func TestOptLinkExtension(t *testing.T) {
+	markdown := goldmark.New(
+		goldmark.WithExtensions(
+			New(),
+		),
+	)
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:  "basic option link",
+			input: "[](#opt-systemd.sysusers.enable)",
+			expected: "<p><a class=\"option\" href=\"/?query=systemd.sysusers.enable\">" +
+				"systemd.sysusers.enable</a></p>\n",
+		},
+		{
+			name:  "option link in sentence",
+			input: "You can enable this with [](#opt-systemd.sysusers.enable) in your configuration.",
+			expected: "<p>You can enable this with <a class=\"option\" href=\"/?query=systemd.sysusers.enable\">" +
+				"systemd.sysusers.enable</a> in your configuration.</p>\n",
+		},
+		{
+			name:  "multiple option links",
+			input: "Both [](#opt-systemd.sysusers.enable) and [](#opt-networking.firewall.enable) can be used.",
+			expected: "<p>Both <a class=\"option\" href=\"/?query=systemd.sysusers.enable\">" +
+				"systemd.sysusers.enable</a> and <a class=\"option\" href=\"/?query=networking.firewall.enable\">" +
+				"networking.firewall.enable</a> can be used.</p>\n",
+		},
+		{
+			name:     "not an option link - normal link",
+			input:    "[regular link](https://example.com)",
+			expected: "<p><a href=\"https://example.com\">regular link</a></p>\n",
+		},
+		{
+			name:     "not an option link - empty link with different format",
+			input:    "[](#other-prefix)",
+			expected: "<p><a href=\"#other-prefix\"></a></p>\n",
+		},
+		{
+			name:  "option link with special characters",
+			input: "[](#opt-users.users.<n>.hashedPassword)",
+			expected: "<p><a class=\"option\" href=\"/?query=users.users.%3Cn%3E.hashedPassword\">" +
+				"users.users.&lt;n&gt;.hashedPassword</a></p>\n",
+		},
+		{
+			name:  "option link with normal link in sentence",
+			input: "Use [](#opt-networking.firewall.enable) and see [the docs](https://nixos.org) for more information.",
+			expected: "<p>Use <a class=\"option\" href=\"/?query=networking.firewall.enable\">" +
+				"networking.firewall.enable</a> and see <a href=\"https://nixos.org\">the docs</a> for more information.</p>\n",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			if err := markdown.Convert([]byte(test.input), &buf); err != nil {
+				t.Fatalf("Failed to convert markdown: %v", err)
+			}
+
+			if got := buf.String(); got != test.expected {
+				t.Errorf("Expected:\n%q\nGot:\n%q", test.expected, got)
+			}
+		})
+	}
+}
+
+func TestOptLinkNodeKind(t *testing.T) {
+	n := &Node{}
+	if kind := n.Kind(); kind != KindOptLink {
+		t.Errorf("Expected node kind %v, got %v", KindOptLink, kind)
+	}
+	if !n.Inline() {
+		t.Error("Expected node to be inline")
+	}
+}