Add unit tests

Makefile

@@ -67,7 +67,9 @@ juju-unit-test:
 .PHONY: envtestlxd
 envtestlxd:
 ## envtestlxd: Under development - Include env var and run unit tests against lxd
-	JUJU_CONTROLLER_ADDRESSES=${CONTROLLER_ADDRESSES} JUJU_USERNAME=${USERNAME} JUJU_PASSWORD=${PASSWORD} JUJU_CA_CERT=${CA_CERT} TF_ACC=1 TEST_CLOUD=lxd go test ./... -v $(TESTARGS) -timeout 120m
+	JUJU_CONTROLLER_ADDRESSES=${CONTROLLER_ADDRESSES} \
+	JUJU_USERNAME=${USERNAME} JUJU_PASSWORD=${PASSWORD} \
+	JUJU_CA_CERT=${CA_CERT} TF_ACC=1 TEST_CLOUD=lxd go test ./... -v $(TESTARGS) -timeout 120m
 
 .PHONY: testlxd
 testlxd:

internal/provider/resource_application.go

@@ -240,7 +240,7 @@ func (r *applicationResource) Schema(_ context.Context, _ resource.SchemaRequest
 								stringplanmodifier.UseStateForUnknown(),
 							},
 							Validators: []validator.String{
-								stringIsChannelValidator{},
+								StringIsChannelValidator{},
 							},
 						},
 						"revision": schema.Int64Attribute{

internal/provider/validator_channel.go

@@ -10,26 +10,33 @@ import (
 	"github.com/juju/charm/v11"
 )
 
-type stringIsChannelValidator struct{}
+type StringIsChannelValidator struct{}
 
 // Description returns a plain text description of the validator's behavior, suitable for a practitioner to understand its impact.
-func (v stringIsChannelValidator) Description(context.Context) string {
+func (v StringIsChannelValidator) Description(context.Context) string {
 	return "string must conform to track/risk or track/risk/branch e.g. latest/stable"
 }
 
 // MarkdownDescription returns a markdown formatted description of the validator's behavior, suitable for a practitioner to understand its impact.
-func (v stringIsChannelValidator) MarkdownDescription(context.Context) string {
+func (v StringIsChannelValidator) MarkdownDescription(context.Context) string {
 	return "string must conform to track/risk or track/risk/branch e.g. latest/stable"
 }
 
 // Validate runs the main validation logic of the validator, reading configuration data out of `req` and updating `resp` with diagnostics.
-func (v stringIsChannelValidator) ValidateString(_ context.Context, req validator.StringRequest, resp *validator.StringResponse) {
+func (v StringIsChannelValidator) ValidateString(_ context.Context, req validator.StringRequest, resp *validator.StringResponse) {
 	// If the value is unknown or null, there is nothing to validate.
 	if req.ConfigValue.IsUnknown() || req.ConfigValue.IsNull() {
 		return
 	}
 
-	if channel, err := charm.ParseChannel(req.ConfigValue.ValueString()); err != nil || channel.Track == "" || channel.Risk == "" {
+	if channel, err := charm.ParseChannel(req.ConfigValue.ValueString()); err != nil {
+		resp.Diagnostics.AddAttributeError(
+			req.Path,
+			"Invalid Channel",
+			err.Error(),
+		)
+		return
+	} else if channel.Track == "" || channel.Risk == "" {
 		resp.Diagnostics.AddAttributeError(
 			req.Path,
 			"Invalid Channel",

internal/provider/validator_channel_test.go

@@ -0,0 +1,73 @@
+// Copyright 2024 Canonical Ltd.
+// Licensed under the AGPLv3, see LICENCE file for details.
+
+package provider_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/juju/terraform-provider-juju/internal/provider"
+)
+
+func TestChannelValidatorValid(t *testing.T) {
+	validChannels := []types.String{
+		types.StringValue("track/stable"),
+		types.StringValue("track/edge/branch"),
+		types.StringNull(),
+		types.StringUnknown(),
+	}
+
+	channelValidator := provider.StringIsChannelValidator{}
+	for _, channel := range validChannels {
+		req := validator.StringRequest{
+			ConfigValue: channel,
+		}
+		var resp validator.StringResponse
+		channelValidator.ValidateString(context.Background(), req, &resp)
+
+		if resp.Diagnostics.HasError() {
+			t.Errorf("errors %v", resp.Diagnostics.Errors())
+		}
+	}
+}
+
+func TestChannelValidatorInvalid(t *testing.T) {
+	invalidChannels := []struct {
+		str types.String
+		err string
+	}{{
+		str: types.StringValue("track"),
+		err: "String must conform to track/risk or track/risk/branch, e.g. latest/stable",
+	}, {
+		str: types.StringValue("edge"),
+		err: "String must conform to track/risk or track/risk/branch, e.g. latest/stable",
+	}, {
+		str: types.StringValue(`track\risk`),
+		err: "String must conform to track/risk or track/risk/branch, e.g. latest/stable",
+	}, {
+		str: types.StringValue(`track/invalidrisk`),
+		err: `risk in channel "track/invalidrisk" not valid`,
+	}, {
+		str: types.StringValue(`track/invalidrisk/branch`),
+		err: `risk in channel "track/invalidrisk/branch" not valid`,
+	}}
+
+	channelValidator := provider.StringIsChannelValidator{}
+	for _, test := range invalidChannels {
+		req := validator.StringRequest{
+			ConfigValue: test.str,
+		}
+		var resp validator.StringResponse
+		channelValidator.ValidateString(context.Background(), req, &resp)
+
+		if c := resp.Diagnostics.ErrorsCount(); c != 1 {
+			t.Errorf("expected one error, got %d", c)
+		}
+		if deets := resp.Diagnostics.Errors()[0].Detail(); deets != test.err {
+			t.Errorf("expected error %q, got %q", test.err, deets)
+		}
+	}
+}