Debug Cucumber Tests in Emacs

debug cucumber-js tests in emacs with dap-mode

test example

TMP="$(mktemp -d)"
trap "rm -rf '${TMP}'" 0

git clone https://github.com/cucumber/cucumber-js-examples "${TMP}"

Cloning into '/home/sam/tmp/tmp.xmxvENC75r'...
remote: Enumerating objects: 195, done.
remote: Counting objects:   4% (1/25)        
remote: Counting objects:   8% (2/25)        
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remote: Counting objects: 100% (25/25), done.
remote: Compressing objects:  10% (1/10)        
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remote: Compressing objects:  90% (9/10)        
remote: Compressing objects: 100% (10/10)        
remote: Compressing objects: 100% (10/10), done.
Receiving objects:   0% (1/195)
Receiving objects:   1% (2/195)
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remote: Total 195 (delta 16), reused 15 (delta 15), pack-reused 170
Receiving objects:  97% (190/195)
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Receiving objects: 100% (195/195)
Receiving objects: 100% (195/195), 236.99 KiB | 955.00 KiB/s, done.
Resolving deltas:   0% (0/61)
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Resolving deltas: 100% (61/61)
Resolving deltas: 100% (61/61), done.

cd "${TMP}/examples/command-line"

npm i

added 90 packages, and audited 91 packages in 6s

7 packages are looking for funding
  run `npm fund` for details

1 high severity vulnerability

To address all issues, run:
  npm audit fix

Run `npm audit` for details.

npm test

> command-line-cucumber-js-example@1.0.0 test
> cucumber-js

/home/sam/tmp/tmp.xmxvENC75r/examples/command-line/bin
greet hello
[32m.[39m[32m.[39m

1 scenario ([32m1 passed[39m)
2 steps ([32m2 passed[39m)
0m00.251s (executing steps: 0m00.204s)

running with default dap-node (spoiler, it won’t work)

Getting into the step and adding a breakpoint

Then, using dap-node.

(load-library "dap-node")

It comes with a default “Node Run Configuration” template.

I need to extend it to tell the command to run and where to run the command from¹.

{ “name”: “Launch dev acceptance tests”, “type”: “pwa-node”, “request”: “launch”, “program”: “${workspaceRoot}/node_modules/.bin/cucumber-js”, “skipFiles”: [ “${workspaceRoot}/node_modules/**/*.js” ], “cwd”: “${workspaceRoot}/test”, “args”: ["–tags", “@only”,"-p", “no_headless”, “–parallel”, “1”], },

(dap-register-debug-template "Debug the example"
                             (list :type "node"
                                   :cwd "${workspaceFolder}"
                                   :request "launch"
                                   :program (string-trim (shell-command-to-string "which npm"))
                                   :args ["test"]
                                   :name "Node::Run"))

Then, with the steps.js buffer open, dun

In the output buffer, I get

node --inspect-brk=44822 ../../../../n/bin/npm test
Starting inspector on 127.0.0.1:44822 failed: address already in use

This is likely due to the fact cucumber spawns children processes and the obsolete debugger ms-vscode.node-debug2.

using dap-js-debug from https://github.com/emacs-lsp/dap-mode/pull/736

See https://github.com/emacs-lsp/dap-mode/issues/369 for more information.

(load-library "dap-js-debug")

It will match the "type": "pwa-node", instead of "type": "node", (see pwa-node vs node type).

So we need to use another template (based on the one already given in dap-js-debug.el).

(dap-register-debug-template "Debug the template"
                             (list :type "pwa-node"
                                   :cwd "${workspaceFolder}"
                                   :request "launch"
                                   :program (string-trim (shell-command-to-string "which npm"))
                                   :args ["test"]
                                   :name "Node.js Launch Program"))

Now, it works great!

Notes linking here

Permalink

note that I can make use of the Visual Studio Code variables, but the likes of workspaceFolder will work only if lsp is enabled and the root it’s root is appropriate.
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