test: add template error test (#12489)

template/template_test.go

@@ -154,24 +154,55 @@ func TestTemplate(t *testing.T) {
 }
 
 func TestParse(t *testing.T) {
-	cases := []struct {
+	validCases := []struct {
+		name     string
 		template string
 		vars     []string
 	}{
-		{"{{ .Prompt }}", []string{"prompt", "response"}},
-		{"{{ .System }} {{ .Prompt }}", []string{"prompt", "response", "system"}},
-		{"{{ .System }} {{ .Prompt }} {{ .Response }}", []string{"prompt", "response", "system"}},
-		{"{{ with .Tools }}{{ . }}{{ end }} {{ .System }} {{ .Prompt }}", []string{"prompt", "response", "system", "tools"}},
-		{"{{ range .Messages }}{{ .Role }} {{ .Content }}{{ end }}", []string{"content", "messages", "role"}},
-		{"{{ range .Messages }}{{ if eq .Role \"tool\" }}Tool Result: {{ .ToolName }} {{ .Content }}{{ end }}{{ end }}", []string{"content", "messages", "role", "toolname"}},
-		{`{{- range .Messages }}
+		{
+			name:     "PromptOnly",
+			template: "{{ .Prompt }}",
+			vars:     []string{"prompt", "response"},
+		},
+		{
+			name:     "SystemAndPrompt",
+			template: "{{ .System }} {{ .Prompt }}",
+			vars:     []string{"prompt", "response", "system"},
+		},
+		{
+			name:     "PromptResponseSystem",
+			template: "{{ .System }} {{ .Prompt }} {{ .Response }}",
+			vars:     []string{"prompt", "response", "system"},
+		},
+		{
+			name:     "ToolsBlock",
+			template: "{{ with .Tools }}{{ . }}{{ end }} {{ .System }} {{ .Prompt }}",
+			vars:     []string{"prompt", "response", "system", "tools"},
+		},
+		{
+			name:     "MessagesRange",
+			template: "{{ range .Messages }}{{ .Role }} {{ .Content }}{{ end }}",
+			vars:     []string{"content", "messages", "role"},
+		},
+		{
+			name:     "ToolResultConditional",
+			template: "{{ range .Messages }}{{ if eq .Role \"tool\" }}Tool Result: {{ .ToolName }} {{ .Content }}{{ end }}{{ end }}",
+			vars:     []string{"content", "messages", "role", "toolname"},
+		},
+		{
+			name: "MultilineSystemUserAssistant",
+			template: `{{- range .Messages }}
 {{- if eq .Role "system" }}SYSTEM:
 {{- else if eq .Role "user" }}USER:
 {{- else if eq .Role "assistant" }}ASSISTANT:
-{{- else if eq .Role "tool" }}TOOL: 
+{{- else if eq .Role "tool" }}TOOL:
 {{- end }} {{ .Content }}
-{{- end }}`, []string{"content", "messages", "role"}},
-		{`{{- if .Messages }}
+{{- end }}`,
+			vars: []string{"content", "messages", "role"},
+		},
+		{
+			name: "ChatMLLike",
+			template: `{{- if .Messages }}
 {{- range .Messages }}<|im_start|>{{ .Role }}
 {{ .Content }}<|im_end|>
 {{ end }}<|im_start|>assistant
@@ -182,22 +213,60 @@ func TestParse(t *testing.T) {
 {{ .Prompt }}<|im_end|>
 {{ end }}<|im_start|>assistant
 {{ .Response }}<|im_end|>
-{{- end -}}`, []string{"content", "messages", "prompt", "response", "role", "system"}},
+{{- end -}}`,
+			vars: []string{"content", "messages", "prompt", "response", "role", "system"},
+		},
 	}
 
-	for _, tt := range cases {
-		t.Run("", func(t *testing.T) {
+	for _, tt := range validCases {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			tmpl, err := Parse(tt.template)
 			if err != nil {
-				t.Fatal(err)
+				t.Fatalf("Parse returned unexpected error: %v", err)
 			}
 
-			v, err := tmpl.Vars()
+			gotVars, err := tmpl.Vars()
 			if err != nil {
-				t.Fatal(err)
+				t.Fatalf("Vars returned unexpected error: %v", err)
 			}
-			if diff := cmp.Diff(v, tt.vars); diff != "" {
-				t.Errorf("mismatch (-got +want):\n%s", diff)
+
+			if diff := cmp.Diff(gotVars, tt.vars); diff != "" {
+				t.Errorf("Vars mismatch (-got +want):\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestParseError(t *testing.T) {
+	invalidCases := []struct {
+		name     string
+		template string
+		errorStr string
+	}{
+		{
+			"TemplateNotClosed",
+			"{{ .Prompt ",
+			"unclosed action",
+		},
+		{
+			"Template",
+			`{{define "x"}}{{template "x"}}{{end}}{{template "x"}}`,
+			"undefined template specified",
+		},
+	}
+
+	for _, tt := range invalidCases {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := Parse(tt.template)
+			if err == nil {
+				t.Fatalf("expected Parse to return an error for an invalid template, got nil")
+			}
+
+			if !strings.Contains(strings.ToLower(err.Error()), strings.ToLower(tt.errorStr)) {
+				t.Errorf("unexpected error message.\n got: %q\n want substring (case‑insensitive): %q", err.Error(), tt.errorStr)
 			}
 		})
 	}