Argument Captors

Argument captors are a powerful feature that allow you to capture the arguments passed to a method when it is called. This is useful when you want to verify that a method was called with specific arguments, but you don't know what those arguments will be ahead of time.

Creating a Captor

To create a captor, you simply call the Captor function with the type of the argument you want to capture:

Go

c := Captor[string]()

Using a Captor

To use a captor, you pass it as an argument to the When function. When the method is called, the captor will capture the argument and store it in the captor's value:

Go

When(greeter.Greet(c.Capture())).ThenReturn("Hello, world!")

Retrieving the Captured Values

Argument captor records an argument on each stub call. You can retrieve the captured values by calling the Values method

Go

capturedValues := c.Values()

If you want to retrieve just the last captured value, you can call the Last method

Go

capturedValue := c.Last()

Example usage

In this example we will create a mock, and use an argument captor to capture the arguments passed to the Greet method:

Go

package main

import (
    . "github.com/ovechkin-dm/mockio/mock"
    "testing"
)

type Greeter interface {
    Greet(name any) string
}

func TestSimple(t *testing.T) {
    SetUp(t)
    greeter := Mock[Greeter]()
    c := Captor[string]()
    When(greeter.Greet(c.Capture())).ThenReturn("Hello, world!")
    _ = greeter.Greet("John")
    _ = greeter.Greet("Jane")
    if c.Values()[0] != "John" {
        t.Error("Expected John, got", c.Values()[0])
    }
    if c.Values()[1] != "Jane" {
        t.Error("Expected Jane, got", c.Values()[1])
    }
}