MockConsole

MockConsole provides a testable interface for programs interacting with the console by modeling input and output as reading from and writing to intput and output buffers maintained by MockConsole and backed by a Ref.

All calls to putStr and putStrLn using the MockConsole will write the string to the output buffer and all calls to getStrLn will take a string from the input buffer. No actual printing or reading from the console will occur. MockConsole has several methods to access and manipulate the content of these buffers including feedLines to feed strings to the input buffer that will then be returned by calls to getStrLn, output to get the content of the output buffer from calls to putStr and putStrLn, and clearInput and clearOutput to clear the respective buffers.

Together, these functions make it easy to test programs interacting with the console.

import zio.console._
import zio.test.mock._
import zio.ZIO

val sayHello = for {
  name <- getStrLn
  _    <- putStrLn("Hello, " + name + "!")
} yield ()

for {
  _ <- MockConsole.feedLines("John", "Jane", "Sally")
  _ <- ZIO.collectAll(List.fill(3)(sayHello))
  result <- MockConsole.output
} yield result == Vector("Hello, John!\n", "Hello, Jane!\n", "Hello, Sally!\n")