@@ -0,0 +1,78 @@
+package envvar
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/yuin/goldmark"
+)
+
+func TestEnvExtension(t *testing.T) {
+	markdown := goldmark.New(
+		goldmark.WithExtensions(
+			New(),
+		),
+	)
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "basic env variable reference",
+			input:    "{env}`XDG_DATA_DIRS`",
+			expected: "<p><span class=\"envvar\">XDG_DATA_DIRS</span></p>\n",
+		},
+		{
+			name:     "env variable reference in sentence",
+			input:    "The environment variable {env}`PATH` contains a list of directories.",
+			expected: "<p>The environment variable <span class=\"envvar\">PATH</span> contains a list of directories.</p>\n",
+		},
+		{
+			name:  "multiple env variable references",
+			input: "Both {env}`HOME` and {env}`XDG_CONFIG_HOME` define user directories.",
+			expected: "<p>Both <span class=\"envvar\">HOME</span> and <span class=\"envvar\">" +
+				"XDG_CONFIG_HOME</span> define user directories.</p>\n",
+		},
+		{
+			name:     "incomplete env variable reference - no closing backtick",
+			input:    "{env}`MISSING_BACKTICK",
+			expected: "<p>{env}`MISSING_BACKTICK</p>\n",
+		},
+		{
+			name:     "incomplete env variable reference - empty variable name",
+			input:    "{env}``",
+			expected: "<p>{env}``</p>\n",
+		},
+		{
+			name:  "env variable reference with code block",
+			input: "Set {env}`GOPATH` in your `~/.bashrc` file.",
+			expected: "<p>Set <span class=\"envvar\">GOPATH</span> " +
+				"in your <code>~/.bashrc</code> file.</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 TestEnvNodeKind(t *testing.T) {
+	n := &Node{}
+	if kind := n.Kind(); kind != KindEnv {
+		t.Errorf("Expected node kind %v, got %v", KindEnv, kind)
+	}
+	if !n.Inline() {
+		t.Error("Expected node to be inline")
+	}
+}