BoxTest.java

package com.bobocode.basics;

import lombok.SneakyThrows;
import org.junit.jupiter.api.*;

import static org.assertj.core.api.Assertions.assertThat;

@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class BoxTest {
	private final String TYPE_PARAMETER_NAME = "T";

	@Test
	@Order(1)
	@DisplayName("Box class has one type parameter")
	void boxClassHasOneTypeParameter() {
		var typeParameters = Box.class.getTypeParameters();

		assertThat(typeParameters.length).isEqualTo(1);
	}

	@Test
	@Order(2)
	@DisplayName("Type parameter is called \"T\"")
	void typeParameterIsCalledT() {
		var typeParameter = Box.class.getTypeParameters()[0];

		assertThat(typeParameter.getName()).isEqualTo(TYPE_PARAMETER_NAME);
	}

	@Test
	@Order(3)
	@DisplayName("Type parameter \"T\" is not bounded")
	void typeParameterIsNotBounded() {
		var typeParameter = Box.class.getTypeParameters()[0];

		assertThat(typeParameter.getBounds()).hasSize(1);
		assertThat(typeParameter.getBounds()[0].getTypeName()).isEqualTo(Object.class.getTypeName());
	}

	@Test
	@SneakyThrows
	@Order(4)
	@DisplayName("Field \"value\" is \"T\"")
	void valueFieldIsGeneric() {
		var valueField = Box.class.getDeclaredField("value");
		var genericType = valueField.getGenericType();

		assertThat(genericType.getTypeName()).isEqualTo(TYPE_PARAMETER_NAME);
	}

	@Test
	@SneakyThrows
	@Order(5)
	@DisplayName("Constructor parameter type is \"T\"")
	void constructorParameterIsGeneric() {
		var constructor = Box.class.getDeclaredConstructors()[0];
		assert (constructor.getParameters().length == 1);
		var parameter = constructor.getParameters()[0];

		assertThat(parameter.getParameterizedType().getTypeName()).isEqualTo(TYPE_PARAMETER_NAME);
	}

	@Test
	@SneakyThrows
	@Order(6)
	@DisplayName("Getter return type is \"T\"")
	void getterReturnTypeIsGeneric() {
		var getter = Box.class.getDeclaredMethod("getValue");

		assertThat(getter.getGenericReturnType().getTypeName()).isEqualTo(TYPE_PARAMETER_NAME);
	}

	@Test
	@SneakyThrows
	@Order(7)
	@DisplayName("Setter parameter type is \"T\"")
	void setterParameterIsGeneric() {
		var setter = Box.class.getDeclaredMethod("setValue", Object.class);
		assert (setter.getParameters().length == 1);
		var parameter = setter.getParameters()[0];

		assertThat(parameter.getParameterizedType().getTypeName()).isEqualTo(TYPE_PARAMETER_NAME);
	}
}