Gno Test

There are two methods for testing a realm or package during the development phase:

1. Calling the realm/package after deploying it on a local network (or testnet).
2. Using the test option within the gno CLI.

While the first method is recommended for its accuracy and similarity to the actual deployment environment, it is more efficient to initially utilize the second method for composing test cases and then proceed to the first method if no errors are detected.

This section will teach you how to use the second method.

Writing test cases in Gno is similar to that of Go, with general rules as the following:

• Test file naming conventions must be adhered to (ex: xxx_test.gno).
• Test functions must start with Test.
• The t *testing.T argument must be included in each test function.
  • The testing package must be imported.
• Tests must be run with the gno test command.

Let's write a sample code and test it.

// contract.gno

package demo

func Hello(name string) string {
    return "Hello " + name + "!"
}

This is a simple code that returns the string-typed argument in a specific format.

Next, we'll write a test case that looks like the following:

// contract_test.gno

package demo

import "testing"

func TestHello(t *testing.T) {
  {
    got := Hello("People")
    expected := "Hello People!"
    if got != expected {
        t.Fatalf("expected %q, got %q.", expected, got)
    }
  }
  {
    got := Hello("")
    expected := "Hello People!"
    if got != expected {
        t.Fatalf("expected %q, got %q.", expected, got)
    }
  }
}

Two conditions exist in the test case above.

1. "Hello People!" should be returned when calling Hello("People").
2. "Hello People!" should be returned when calling Hello("").

Upon examination of our realm code and the associated test results, the initial condition exhibited the desired behavior; however, an error was identified in the second condition. Despite the expected outcome of "Hello" being returned, the test case incorrectly specified that the expected output should be "Hello People!" instead.

Replacing the second test case with the following will successfully fix the issue and allow the test to pass.

  {
    got := Hello("")
    expected := "Hello !"
    if expected != got {
        t.Fatalf("expected %q, got %q.", expected, got)
    }
  }

Blockchain context in tests

Running gno test executes files within the directory that end with _test.gno and _filetest.gno. Internally, a GnoVM instance is initialized to run the test, and, at that moment, a blockchain-related context is injected into the GnoVM. Utilizing this context, the transaction sender, coins, block height, etc. can be mocked.

For detailed information on these functions, refer to their reference page.