2. Add unit tests using `goopstest`¶

In this section, we will write unit tests for the charm using goopstest. This step of the tutorial assumes you have completed the previous step.

2.1 Write the unit tests¶

2.1.1 Status is blocked given invalid port configuration¶

Here we will write a unit test that validates that the unit stauts is blocked given an invalid configuration. Create a new file internal/charm/charm_test.go with the following content:

package charm_test

import (
    "myapp-k8s-operator/internal/charm"
    "testing"

    "github.com/gruyaume/goops/goopstest"
)

func TestGivenBadPortConfigWhenAnyEventThenStatusBlocked(t *testing.T) {
    ctx := goopstest.NewContext(
        charm.Configure,
    )
    stateIn := goopstest.State{
        Config: map[string]any{
            "port": 0, // Invalid port
        },
        Containers: []goopstest.Container{
            {
                Name:       "myapp",
                CanConnect: true,
            },
        },
    }

    stateOut := ctx.Run("update-status", stateIn)

    expectedStatus := goopstest.Status{
        Name:    goopstest.StatusBlocked,
        Message: "invalid config: port must be between 1 and 65535",
    }
    if stateOut.UnitStatus != expectedStatus {
        t.Errorf("expected status %v, got %v", expectedStatus, stateOut.UnitStatus)
    }
}

2.1.2 Status is active given valid configuration¶

Now, we will write a unit test that validates that the unit status is active given a valid configuration. Add the following test to the same file:

func TestGivenValidConfigWhenAnyEventThenStatusActive(t *testing.T) {
    ctx := goopstest.NewContext(
        charm.Configure,
    )
    stateIn := goopstest.State{
        Config: map[string]any{
            "port": 8080,
        },
        Containers: []goopstest.Container{
            {
                Name:       "myapp",
                CanConnect: true,
            },
        },
    }

    stateOut := ctx.Run("update-status", stateIn)

    expectedStatus := goopstest.Status{
        Name:    goopstest.StatusActive,
        Message: "service is running on port 8080",
    }
    if stateOut.UnitStatus != expectedStatus {
        t.Errorf("expected status %v, got %v", expectedStatus, stateOut.UnitStatus)
    }
}

2.1.3 Pebble layer is added given valid configuration¶

Finally, we will write a unit test that validates that the Pebble layer is added when the configuration is valid. Add the following test to the same file:

func TestGivenValidConfigWhenAnyEventThenPebbleLayerIsAdded(t *testing.T) {
    ctx := goopstest.NewContext(
        charm.Configure,
    )
    stateIn := goopstest.State{
        Config: map[string]any{
            "port": 8080, // Valid port
        },
        Containers: []goopstest.Container{
            {
                Name:       "myapp",
                CanConnect: true,
            },
        },
    }

    stateOut := ctx.Run("update-status", stateIn)

    got := stateOut.Containers[0].Layers["myapp"]

    want := goopstest.Layer{
        Summary:     "MyApp layer",
        Description: "pebble config layer for MyApp",
        Services: map[string]goopstest.Service{
            "myapp": {
                Summary:  "My App Service",
                Command:  "myapp -config /etc/myapp/config.yaml",
                Startup:  "enabled",
                Override: "replace",
            },
        },
    }

    if diff := cmp.Diff(want, got); diff != "" {
        t.Errorf("unexpected pebble layer (-want +got):\n%s", diff)
    }
}

Update the import statement at the top of the file to include the cmp package:

import (
    "github.com/google/go-cmp/cmp"
)

Update the packages:

go mod tidy

2.2 Run the tests¶

Run the tests using the go test command:

go test -cover ./...

You should see output indicating that the tests passed:

guillaume@courge:~/code/myapp-k8s-operator$ go test -cover ./...
        myapp-k8s-operator/cmd/myapp-k8s-operator               coverage: 0.0% of statements
ok      myapp-k8s-operator/internal/charm       (cached)        coverage: 75.0% of statements

2. Add unit tests using goopstest¶