add more tests

fixtures/alt

@@ -0,0 +1 @@
+<esi:include src="http://invalid.do.main" alt=http://domain.com:9080/alt-esi-include/>

fixtures/include

@@ -1 +1 @@
-<esi:include src="http://domain.com/chained-esi-include-1" alt=http://domain.com/alt-esi-include/>
+<esi:include src="http://domain.com:9080/chained-esi-include-1" alt=http://domain.com:9080/alt-esi-include/>

middleware/caddy/esi_test.go

@@ -34,3 +34,26 @@ func TestFullHTML(t *testing.T) {
 
 	_, _ = tester.AssertGetResponse(`http://domain.com:9080/full.html`, http.StatusOK, expectedOutput)
 }
+
+func TestInclude(t *testing.T) {
+	tester := caddytest.NewTester(t)
+	tester.InitServer(loadCaddyfile(), "caddyfile")
+
+	_, _ = tester.AssertGetResponse(`http://domain.com:9080/include`, http.StatusOK, "<h1>CHAINED 2</h1>")
+}
+
+func TestIncludeAlt(t *testing.T) {
+	tester := caddytest.NewTester(t)
+	tester.InitServer(loadCaddyfile(), "caddyfile")
+
+	_, _ = tester.AssertGetResponse(`http://domain.com:9080/alt`, http.StatusOK, "<h1>ALTERNATE ESI INCLUDE</h1>")
+}
+
+func TestEscape(t *testing.T) {
+	tester := caddytest.NewTester(t)
+	tester.InitServer(loadCaddyfile(), "caddyfile")
+
+	_, _ = tester.AssertGetResponse(`http://domain.com:9080/escape`, http.StatusOK, `  
+  <p><esi:vars>Hello, $(HTTP_COOKIE{name})!</esi:vars></p>
+`)
+}