Clarify appending in Rust write-test prompt

Author: bauersimon

model/llm/llm.go

@@ -149,6 +149,9 @@ type llmWriteTestSourceFilePromptContext struct {
 // llmWriteTestForFilePromptTemplate is the template for generating an LLM test generation prompt.
 var llmWriteTestForFilePromptTemplate = template.Must(template.New("model-llm-write-test-for-file-prompt").Parse(bytesutil.StringTrimIndentations(`
 	Given the following {{ .Language.Name }} code file "{{ .FilePath }}" {{- with .ImportPath }} with package "{{ . }}" {{- end }}, {{- if .HasTestsInSource }} provide tests for this code that can be appended to the source file{{ else }} provide a test file for this code{{ with .TestFramework }} with {{ . }} as a test framework{{ end }}{{ end -}}.
+	{{- if .HasTestsInSource }}
+	Add everything required for testing, but do not repeat the original file and do not try to import the code file.
+	{{- end }}
 	The tests should produce 100 percent code coverage and must compile.
 	The response must contain only the test code in a fenced code block and nothing else.
 

model/llm/llm_test.go

@@ -709,6 +709,7 @@ func TestFormatPromptContext(t *testing.T) {
 
 			ExpectedMessage: bytesutil.StringTrimIndentations(`
 				Given the following Rust code file "path/to/main.rs", provide tests for this code that can be appended to the source file.
+				Add everything required for testing, but do not repeat the original file and do not try to import the code file.
 				The tests should produce 100 percent code coverage and must compile.
 				The response must contain only the test code in a fenced code block and nothing else.