Add test for nil address and add tests for TestIsGroupAddress.

app/group.go

@@ -17,6 +17,9 @@ type GroupPolicyQuerier interface {
 
 // IsGroupAddress checks if the account is a group address.
 func (t GroupCheckerFunc) IsGroupAddress(ctx sdk.Context, account sdk.AccAddress) bool {
+	if account == nil {
+		return false
+	}
 	return t(ctx, account)
 }
 

app/group_test.go

@@ -1,14 +1,72 @@
 package app
 
-import "testing"
+import (
+	"context"
+	"testing"
 
-type MockGroupPolicyQuerier struct {
-}
+	"github.com/stretchr/testify/assert"
+
+	cerrs "cosmossdk.io/errors"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/group"
+	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
+)
 
 func TestNewGroupCheckerFunc(t *testing.T) {
 
 }
 
 func TestIsGroupAddress(t *testing.T) {
+	tests := []struct {
+		name         string
+		querySuccess bool
+		address      sdk.AccAddress
+	}{
+		{
+			name:         "should be true with group address",
+			querySuccess: true,
+			address:      sdk.AccAddress("test"),
+		},
+		{
+			name:         "should return false with non group address",
+			querySuccess: false,
+			address:      sdk.AccAddress("test"),
+		},
+		{
+			name:         "should return false with nil address",
+			querySuccess: false,
+			address:      nil,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			querier := NewMockGroupPolicyQuerier(tc.querySuccess)
+			checker := NewGroupCheckerFunc(querier)
+			ctx := sdk.NewContext(nil, tmproto.Header{}, true, nil)
+			success := checker.IsGroupAddress(ctx, tc.address)
+			assert.Equal(t, tc.querySuccess, success, "should correctly detect if the supplied address is a group address")
+		})
+	}
+}
+
+// MockGroupPolicyQuerier mocks the querier so a GroupKeeper isn't needed.
+type MockGroupPolicyQuerier struct {
+	isGroupAddress bool
+}
+
+// NewMockGroupPolicyQuerier creates a new MockGroupPolicyQuerier.
+func NewMockGroupPolicyQuerier(isGroupAddress bool) *MockGroupPolicyQuerier {
+	return &MockGroupPolicyQuerier{
+		isGroupAddress: isGroupAddress,
+	}
+}
 
+// GroupPolicyInfo provides a stubbed implementation of the GroupPolicyInfo method.
+func (t MockGroupPolicyQuerier) GroupPolicyInfo(goCtx context.Context, request *group.QueryGroupPolicyInfoRequest) (*group.QueryGroupPolicyInfoResponse, error) {
+	var err error
+	if !t.isGroupAddress {
+		err = cerrs.New("", 1, "")
+	}
+	return nil, err
 }