Scala Development

Name: Scala Development
Rating: 76
Author: channingwalton

Principles

•Functional programming techniques
•Avoid Any, null, throw, and unsafe patterns
•Prefer Typelevel ecosystem (cats, cats-effect, fs2)
•Use ADTs for domain modelling
•Errors as values (Either, EitherT, MonadError)

Compilation Priority

•Check for .bloop directory first (ls -la)

If .bloop exists — use bloop:

bash

bloop compile <module-name>
bloop test <module-name>
bloop test <module-name> -o "*<filename>*"

Module name is root for non-modular projects.

If no .bloop — use sbt:

bash

sbt compile
sbt test
sbt "testOnly *SpecName*"

•ALWAYS run sbt commitCheck after completing code changes.

Testing (MUnit)

scala

class FeatureSpec extends munit.FunSuite:

  test("describes expected behaviour") {
    // Arrange
    val input = createTestData()

    // Act
    val result = functionUnderTest(input)

    // Assert
    assertEquals(result, expected)
  }

Effectful tests (cats-effect):

scala

class FeatureSpec extends munit.CatsEffectSuite:

  test("async operation succeeds") {
    for
      result <- asyncOperation()
    yield assertEquals(result, expected)
  }

Assertions:

•assertEquals(obtained, expected)
•assertNotEquals(obtained, unexpected)
•assert(condition)
•interceptMessage[ExceptionType]("message") { code }

Error Handling Patterns

scala

// Prefer Either over exceptions
def parse(input: String): Either[ParseError, Value] = ???

// Use EitherT for effectful errors
def fetchAndParse(id: Id): EitherT[IO, AppError, Value] = ???

// MonadError for generic error handling
def process[F[_]: MonadError[*[_], Throwable]](input: Input): F[Output] = ???