refactor: move parse from named struct field tag test

cmd/muxt/testdata/generate/form_field_tag.txtar

@@ -0,0 +1,64 @@
+muxt generate --receiver-type=T
+
+cat template_routes.go
+
+exec go test -v
+
+-- template.gohtml --
+{{define "GET / F(form)"}}{{.Data}}{{end}}
+-- go.mod --
+module server
+
+go 1.23
+-- template.go --
+package server
+
+import (
+	"embed"
+	"html/template"
+	"strings"
+)
+
+//go:embed *.gohtml
+var formHTML embed.FS
+
+var templates = template.Must(template.ParseFS(formHTML, "*"))
+
+type (
+	T  struct{}
+	In struct {
+		field string `name:"some-field"`
+	}
+)
+
+func (T) F(form In) string { return strings.ToUpper(form.field + "@") }
+-- template_test.go --
+package server
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func Test(t *testing.T) {
+	mux := http.NewServeMux()
+
+	routes(mux, T{})
+
+	req := httptest.NewRequest(http.MethodGet, "/?some-field=orange", nil)
+	rec := httptest.NewRecorder()
+
+	mux.ServeHTTP(rec, req)
+
+	res := rec.Result()
+
+	if res.StatusCode != http.StatusOK {
+		t.Error("expected OK")
+	}
+
+	if got, exp:=strings.TrimSpace(rec.Body.String()), "ORANGE@"; got != exp {
+		t.Errorf("%q != %q", got, exp)
+	}
+}

internal/muxt/routes_test.go

@@ -560,57 +560,6 @@ func routes(mux *http.ServeMux, receiver RoutesReceiver) {
 		_, _ = buf.WriteTo(response)
 	})
 }
-`,
-		},
-		{
-			Name:      "F is defined and form field has an input tag",
-			Templates: `{{define "GET / F(form)"}}Hello, {{.}}!{{end}}`,
-			ReceiverPackage: `
--- in.go --
-package main
-
-type (
-	T struct{}
-	In struct{
-		field string ` + "`name:\"some-field\"`" + `
-	}
-)
-
-func (T) F(form In) int { return 0 }
-`,
-			Receiver: "T",
-			ExpectedFile: `package main
-
-import (
-	"bytes"
-	"net/http"
-)
-
-type RoutesReceiver interface {
-	F(form In) int
-}
-
-func routes(mux *http.ServeMux, receiver RoutesReceiver) {
-	mux.HandleFunc("GET /", func(response http.ResponseWriter, request *http.Request) {
-		type ResponseData struct {
-			Data    int
-			Request *http.Request
-		}
-		request.ParseForm()
-		var form In
-		form.field = request.FormValue("some-field")
-		data := receiver.F(form)
-		buf := bytes.NewBuffer(nil)
-		rd := ResponseData{Data: data, Request: request}
-		if err := templates.ExecuteTemplate(buf, "GET / F(form)", rd); err != nil {
-			http.Error(response, err.Error(), http.StatusInternalServerError)
-			return
-		}
-		response.Header().Set("content-type", "text/html; charset=utf-8")
-		response.WriteHeader(http.StatusOK)
-		_, _ = buf.WriteTo(response)
-	})
-}
 `,
 		},
 		{