Running Backend Server

To collect code coverage for a Node.js backend application, the SeaLights Node.js agent can be attached in one of two ways:

• Non-Intrusive Approach (Using preload.js with NODE_OPTIONS)

• Wrapper Command (Using slnodejs run)

Once your application starts with the agent, it should appear under Live Agents Monitor in the SeaLights Cockpit.

Non-Intrusive Approach (Using preload.js with NODE_OPTIONS)

This method is ideal when you cannot or prefer not to modify the application’s execution command, such as in Docker containers, pm2, or CI environments.

The SeaLights agent provides a preload.js script that can be injected into the process using the NODE_OPTIONS environment variable.

export SL_tokenfile=./sltoken.txt
export SL_buildsessionidfile=buildSessionId
export SL_labid=my_lab_id
export NODE_OPTIONS="--require ./node_modules/slnodejs/lib/preload.js"

node ./server/app.js

💡 Note: This method also works with TypeScript apps run via ts-node, e.g., ts-node ./server/app.ts. No special handling is needed beyond setting NODE_OPTIONS correctly.

Wrapper Command (Using slnodejs run)

This method wraps the application’s startup command using the SeaLights CLI runner. It gives you full control over parameters and visibility into agent behavior.

Generic Node.js App

Unix/Linux

npx slnodejs run --tokenfile ./sltoken.txt --buildsessionidfile buildSessionId --labid my_lab_id --workspacepath ./server --useinitialcolor true -- ./server/app.js

PowerShell

npx slnodejs run --tokenfile .\sltoken.txt --buildsessionidfile buildSessionId --labid my_lab_id --workspacepath .\server --useinitialcolor true -- .\server\app.js

TypeScript App Using ts-node

SeaLights only supports ts-node apps when started with: node -r ts-node/register ./server/app.ts

Wrap this format with the agent:

Linux

npx slnodejs run --tokenfile ./sltoken.txt --buildsessionidfile buildSessionId --labid my_lab_id --workspacepath ./server --useinitialcolor true --useslnode2 -- -r ts-node/register ./server/app.ts

Powershell

npx slnodejs run --tokenfile .\sltoken.txt --buildsessionidfile buildSessionId --labid my_lab_id --workspacepath .\server --useinitialcolor true --useslnode2 -- -r ts-node/register .\server\app.ts

Additional Notes

To verify the agent is running, you can run the following command:

Linux

ps -ef | grep slnodejs

PowerShell

Get-WmiObject Win32_Process | Where-Object { $_.CommandLine -like "*slnodejs*" } | Select-Object CommandLine, ProcessId

• We recommend using the --labid parameter (or SL_labid for preload) to correlate your test and listener sessions. If labid is not set, the session ID will be used automatically.

• For full parameter details, see the Node.js Command Reference.