feat: add HasValidator and Binder validation tests to Checkbox

vaadin-checkbox-flow-parent/vaadin-checkbox-flow-integration-tests/src/main/java/com/vaadin/flow/component/checkbox/tests/validation/CheckboxBinderValidationPage.java

@@ -0,0 +1,43 @@
+package com.vaadin.flow.component.checkbox.tests.validation;
+
+import com.vaadin.flow.component.checkbox.Checkbox;
+import com.vaadin.flow.data.binder.Binder;
+import com.vaadin.flow.router.Route;
+import com.vaadin.tests.validation.AbstractValidationPage;
+
+@Route("vaadin-checkbox/validation/binder")
+public class CheckboxBinderValidationPage
+        extends AbstractValidationPage<Checkbox> {
+
+    public static final String REQUIRED_ERROR_MESSAGE = "The field is required";
+
+    public static class Bean {
+        private Boolean property;
+
+        public Boolean getProperty() {
+            return property;
+        }
+
+        public void setProperty(Boolean property) {
+            this.property = property;
+        }
+    }
+
+    protected Binder<Bean> binder;
+
+    public CheckboxBinderValidationPage() {
+        super();
+
+        binder = new Binder<>(Bean.class);
+        binder.forField(testField).asRequired(REQUIRED_ERROR_MESSAGE)
+                .bind("property");
+        binder.addStatusChangeListener(event -> {
+            incrementServerValidationCounter();
+        });
+    }
+
+    @Override
+    protected Checkbox createTestField() {
+        return new Checkbox();
+    }
+}

vaadin-checkbox-flow-parent/vaadin-checkbox-flow-integration-tests/src/test/java/com/vaadin/flow/component/checkbox/tests/validation/CheckboxBinderValidationIT.java

@@ -0,0 +1,48 @@
+package com.vaadin.flow.component.checkbox.tests.validation;
+
+import com.vaadin.flow.component.checkbox.testbench.CheckboxElement;
+import com.vaadin.flow.testutil.TestPath;
+import com.vaadin.tests.validation.AbstractValidationIT;
+import org.junit.Test;
+import org.openqa.selenium.Keys;
+
+import static com.vaadin.flow.component.checkbox.tests.validation.BinderValidationPage.REQUIRED_ERROR_MESSAGE;
+
+@TestPath("vaadin-checkbox/validation/binder")
+public class CheckboxBinderValidationIT
+        extends AbstractValidationIT<CheckboxElement> {
+
+    @Test
+    public void fieldIsInitiallyValid() {
+        assertClientValid();
+        assertServerValid();
+        assertErrorMessage(null);
+    }
+
+    @Test
+    public void required_triggerBlur_assertValidity() {
+        testField.sendKeys(Keys.TAB);
+        assertValidationCount(0);
+        assertServerValid();
+        assertClientValid();
+    }
+
+    @Test
+    public void required_changeValue_assertValidity() {
+        testField.setChecked(true);
+        assertValidationCount(1);
+        assertServerValid();
+        assertClientValid();
+
+        testField.setChecked(false);
+        assertValidationCount(1);
+        assertServerInvalid();
+        assertClientInvalid();
+        assertErrorMessage(REQUIRED_ERROR_MESSAGE);
+    }
+
+    @Override
+    protected CheckboxElement getTestField() {
+        return $(CheckboxElement.class).first();
+    }
+}

vaadin-checkbox-flow-parent/vaadin-checkbox-flow/src/main/java/com/vaadin/flow/component/checkbox/Checkbox.java

@@ -32,6 +32,7 @@
 import com.vaadin.flow.component.shared.HasValidationProperties;
 import com.vaadin.flow.component.shared.InputField;
 import com.vaadin.flow.component.shared.ValidationUtil;
+import com.vaadin.flow.data.binder.HasValidator;
 import com.vaadin.flow.data.binder.ValidationResult;
 import com.vaadin.flow.data.binder.Validator;
 import com.vaadin.flow.dom.ElementConstants;
@@ -58,7 +59,7 @@
 @JsModule("@vaadin/checkbox/src/vaadin-checkbox.js")
 public class Checkbox extends AbstractSinglePropertyField<Checkbox, Boolean>
         implements ClickNotifier<Checkbox>, Focusable<Checkbox>, HasAriaLabel,
-        HasClientValidation, HasValidationProperties,
+        HasClientValidation, HasValidationProperties, HasValidator<Boolean>,
         InputField<AbstractField.ComponentValueChangeEvent<Checkbox, Boolean>, Boolean> {
 
     private final Label labelElement;

vaadin-checkbox-flow-parent/vaadin-checkbox-flow/src/test/java/com/vaadin/flow/component/checkbox/tests/validation/CheckboxBinderValidationTest.java

@@ -0,0 +1,113 @@
+package com.vaadin.flow.component.checkbox.tests.validation;
+
+import com.vaadin.flow.component.checkbox.Checkbox;
+import com.vaadin.flow.data.binder.Binder;
+import com.vaadin.flow.data.binder.BindingValidationStatus;
+import com.vaadin.flow.data.binder.BindingValidationStatusHandler;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.Ignore;
+
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+
+public class CheckboxBinderValidationTest {
+    private static final String BINDER_FAIL_MESSAGE = "BINDER_FAIL_MESSAGE";
+    private static final String BINDER_REQUIRED_MESSAGE = "REQUIRED";
+
+    private Checkbox field;
+
+    @Captor
+    private ArgumentCaptor<BindingValidationStatus<?>> statusCaptor;
+
+    @Mock
+    private BindingValidationStatusHandler statusHandlerMock;
+
+    public static class Bean {
+        private Boolean value;
+
+        public Boolean getValue() {
+            return value;
+        }
+
+        public void setValue(Boolean value) {
+            this.value = value;
+        }
+    }
+
+    @Before
+    public void init() {
+        MockitoAnnotations.openMocks(this);
+        field = new Checkbox();
+    }
+
+    @Test
+    public void elementWithBinderValidation_invalidValue_binderValidationFails() {
+        var binder = attachBinderToField();
+
+        field.setValue(true);
+        Mockito.verify(statusHandlerMock).statusChange(statusCaptor.capture());
+
+        Assert.assertTrue(statusCaptor.getValue().isError());
+        Assert.assertEquals(BINDER_FAIL_MESSAGE,
+                statusCaptor.getValue().getMessage().orElse(""));
+    }
+
+    @Test
+    public void setRequiredOnBinder_validate_binderValidationFails() {
+        var binder = attachBinderToField(true);
+        binder.validate();
+
+        Mockito.verify(statusHandlerMock).statusChange(statusCaptor.capture());
+        Assert.assertTrue(statusCaptor.getValue().isError());
+        Assert.assertEquals(BINDER_REQUIRED_MESSAGE,
+                statusCaptor.getValue().getMessage().orElse(""));
+    }
+
+    @Test
+    public void setRequiredOnComponent_validate_binderValidationPasses() {
+        var binder = attachBinderToField();
+        field.setRequiredIndicatorVisible(true);
+        binder.validate();
+
+        Mockito.verify(statusHandlerMock).statusChange(statusCaptor.capture());
+        Assert.assertFalse(statusCaptor.getValue().isError());
+    }
+
+    @Test
+    public void setRequiredOnBinder_setValidValue_binderValidationPasses() {
+        attachBinderToField(true);
+
+        field.setValue(true);
+
+        Mockito.verify(statusHandlerMock).statusChange(statusCaptor.capture());
+        Assert.assertFalse(statusCaptor.getValue().isError());
+    }
+
+    private Binder<Bean> attachBinderToField() {
+        return attachBinderToField(false);
+    }
+
+    private Binder<Bean> attachBinderToField(boolean isRequired) {
+        var binder = new Binder<>(Bean.class);
+        var binding = binder.forField(field)
+                .withValidationStatusHandler(statusHandlerMock);
+
+        if (isRequired) {
+            binding.asRequired(BINDER_REQUIRED_MESSAGE);
+        } else {
+            // Consider un-checked as valid
+            binding.withValidator(value -> Boolean.FALSE.equals(value),
+                    BINDER_FAIL_MESSAGE);
+        }
+
+        binding.bind("value");
+
+        return binder;
+    }
+}