如何从 go 项目根文件夹运行测试？

Question

I am working through the text, "Writing an Interpreter in Go" by Thorsten Ball in order to learn about the language.

Project Directory looks like this:

Interpreter/
|---code/
|   |---token/
|   |   |---token.go
|   |   |---go.mod
|   |---lexer/
|       |---lexer_test.go
|       |---go.mod
|---go.mod

I created the go.mod files in this manner

>go mod init monkey
>cd token
>go mod init token
>cd ../lexer
>go mod init lexer

I added this line to the go.mod file in the lexer module

replace monkey/token => ../token

On running go test from inside the lexer folder, I get the expected output as mentioned in the book, but I realize this is not an indicator of the project being setup properly.

>go test
# lexer [lexer.test]
./lexer_test.go:26:7: undefined: New
FAIL    lexer [build failed]

But on running the tests as mentioned in the book, ie from the root folder code in the following manner:

go test ./lexer

go is unable to resolve the lexer package and I get the following error

main module (monkey) does not contain package monkey/lexer

Is there something that needed to be added to the go.mod file in the root folder that fixes this?

Answer 1

As @mkopriva notes, the simple solution is to delete the go.mod files from the token and lexer directories.

In general, a Go project should have a single go.mod file at the project root: each go.mod file indicates a self-contained module.

Answer 2

The solution was

$ cd 01/src/monkey
$ go mod init monkey
$ go test ./lexer