Check if yarn install done before running scripts/test

[udit-gulati]

🛠 Compiling TS files: scripts/sample-script.ts
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scripts/sample-script.ts (3,33): Cannot find module '../artifacts/typescript_schema/CounterContract' or its corresponding type declarations.
Error PE19: Error. Script '/Users/uditgulati/testproject12/build/scripts/sample-script.js' failed during load: Cannot find module '/Users/uditgulati/testproject12/build/scripts/sample-script.js'