Add some more unit tests for the generator

Signed-off-by: Andrea Frittoli <andrea.frittoli@gmail.com>

tools/generator_test.go

@@ -19,8 +19,11 @@ SPDX-License-Identifier: Apache-2.0
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
+	"text/template"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
@@ -107,3 +110,93 @@ func TestDataFromSchema(t *testing.T) {
 		t.Errorf("args: diff(-want,+got):\n%s", d)
 	}
 }
+
+// TestExecuteTemplate_Success verifies that templating and code formatting
+// are both applied
+func TestExecuteTemplate_Success(t *testing.T) {
+	// Template code. The result will be compiled.
+	helloTemplate := `package main
+
+import "fmt"
+func main() {
+    fmt.Println("Hello, {{.Name}}")
+}`
+	// Expected output is the formatted code
+	expectedOutput := `package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello, World")
+}
+`
+
+	// Create a temporary directory to store the generated files
+	tempDir, err := os.MkdirTemp("", "test-execute-template-*")
+	if err != nil {
+		t.Fatalf("error creating temporary directory: %s", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create a template file
+	tmpTemplateFilename := "template.txt.tmpl"
+	templateFile := filepath.Join(tempDir, tmpTemplateFilename)
+	err = os.WriteFile(templateFile, []byte(helloTemplate), 0644)
+	if err != nil {
+		t.Fatalf("error creating template file: %s", err)
+	}
+
+	// Create a template set
+	allTemplates := template.New("all")
+	_, err = allTemplates.ParseFiles(templateFile)
+	if err != nil {
+		t.Fatalf("error parsing template file: %s", err)
+	}
+
+	// Execute the template
+	outputFileName := filepath.Join(tempDir, "output.txt")
+	err = executeTemplate(allTemplates, tmpTemplateFilename, outputFileName, struct{ Name string }{"World"})
+	if err != nil {
+		t.Fatalf("error executing template: %s", err)
+	}
+
+	// Check the output file contents
+	output, err := os.ReadFile(outputFileName)
+	if err != nil {
+		t.Fatalf("error reading output file: %s", err)
+	}
+	if string(output) != expectedOutput {
+		t.Errorf("unexpected output: got %q, want %q", output, expectedOutput)
+	}
+}
+
+// TestExecuteTemplate_Error tests the error case of executeTemplate()
+func TestExecuteTemplate_Error(t *testing.T) {
+	// Create a temporary directory to store the generated files
+	tempDir, err := os.MkdirTemp("", "test-execute-template-*")
+	if err != nil {
+		t.Fatalf("error creating temporary directory: %s", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Create an template file, valid template but invalid go code
+	templateFile := filepath.Join(tempDir, "template.txt")
+	err = os.WriteFile(templateFile, []byte("Hello, {{.Name}}!"), 0644)
+	if err != nil {
+		t.Fatalf("error creating template file: %s", err)
+	}
+
+	// Create a template set
+	allTemplates := template.New("all")
+	_, err = allTemplates.ParseFiles(templateFile)
+	if err != nil {
+		t.Fatalf("error parsing template file: %s", err)
+	}
+
+	// Execute the template
+	outputFileName := filepath.Join(tempDir, "output.txt")
+	err = executeTemplate(allTemplates, "template.txt", outputFileName, struct{ Name string }{"World"})
+	if err == nil {
+		t.Fatal("expected error executing template, got nil")
+	}
+}