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feat: introduce constructor instantiator
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‎src/main/java/com/github/nylle/javafixture/instantiation/Constructor.java‎

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package com.github.nylle.javafixture.instantiation;
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import com.github.nylle.javafixture.CustomizationContext;
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import com.github.nylle.javafixture.SpecimenFactory;
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import com.github.nylle.javafixture.SpecimenType;
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import java.lang.annotation.Annotation;
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import java.lang.reflect.Parameter;
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import java.util.List;
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import java.util.Map;
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import static java.util.Arrays.stream;
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public class Constructor<T> implements Instantiator<T> {
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private final java.lang.reflect.Constructor<T> constructor;
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private Constructor(java.lang.reflect.Constructor<T> constructor) {
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this.constructor = constructor;
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}
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public static <T> Constructor<T> create(java.lang.reflect.Constructor<T> constructor) {
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return new Constructor<>(constructor);
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}
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public T invoke(SpecimenFactory specimenFactory, CustomizationContext customizationContext) {
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try {
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return constructor.newInstance(stream(constructor.getParameters())
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.map(p -> createParameter(p, specimenFactory, customizationContext))
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.toArray());
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} catch(Exception ex) {
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return null;
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}
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}
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private static Object createParameter(Parameter parameter, SpecimenFactory specimenFactory, CustomizationContext customizationContext) {
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if (customizationContext.getIgnoredFields().contains(parameter.getName())) {
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return Primitive.defaultValue(parameter.getType());
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}
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if (customizationContext.getCustomFields().containsKey(parameter.getName())) {
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return customizationContext.getCustomFields().get(parameter.getName());
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}
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return specimenFactory
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.build(SpecimenType.fromClass(parameter.getParameterizedType()))
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.create(new CustomizationContext(List.of(), Map.of(), customizationContext.useRandomConstructor()), new Annotation[0]);
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}
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}

‎src/main/java/com/github/nylle/javafixture/instantiation/Primitive.java‎

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package com.github.nylle.javafixture.instantiation;
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import java.util.Map;
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public class Primitive {
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private static final Map<Class<?>, Object> primitiveDefaults = Map.of(
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Boolean.TYPE, false,
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Character.TYPE, '\0',
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Byte.TYPE, (byte) 0,
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Short.TYPE, 0,
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Integer.TYPE, 0,
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Long.TYPE, 0L,
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Float.TYPE, 0.0f,
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Double.TYPE, 0.0d
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);
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private Primitive() {
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}
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public static Object defaultValue(Class<?> type) {
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return primitiveDefaults.get(type);
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}
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}

‎src/test/java/com/github/nylle/javafixture/instantiation/ConstructorTest.java‎

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package com.github.nylle.javafixture.instantiation;
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import com.github.nylle.javafixture.Configuration;
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import com.github.nylle.javafixture.Context;
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import com.github.nylle.javafixture.CustomizationContext;
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import com.github.nylle.javafixture.SpecimenFactory;
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import com.github.nylle.javafixture.testobjects.TestObject;
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import com.github.nylle.javafixture.testobjects.withconstructor.TestObjectWithConstructedField;
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import com.github.nylle.javafixture.testobjects.withconstructor.TestObjectWithGenericConstructor;
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import org.junit.jupiter.api.DisplayName;
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import org.junit.jupiter.api.Test;
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import java.util.List;
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import java.util.Map;
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import java.util.Optional;
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import static org.assertj.core.api.Assertions.assertThat;
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class ConstructorTest {
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@Test
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@DisplayName("returns instance")
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void canCreateInstanceFromConstructor() throws NoSuchMethodException {
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var sut = Constructor.create(TestObjectWithGenericConstructor.class.getConstructor(String.class, Optional.class));
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of(), Map.of(), false));
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assertThat(actual).isInstanceOf(TestObjectWithGenericConstructor.class);
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assertThat(actual.getValue()).isInstanceOf(String.class);
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assertThat(actual.getInteger()).isInstanceOf(Optional.class);
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}
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@Test
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@DisplayName("fields not set by constructor are null")
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void fieldsNotSetByConstructorAreNull() throws NoSuchMethodException {
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var sut = Constructor.create(TestObjectWithGenericConstructor.class.getConstructor(String.class, Optional.class));
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of(), Map.of(), false));
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assertThat(actual).isInstanceOf(TestObjectWithGenericConstructor.class);
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assertThat(actual.getPrivateField()).isNull();
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}
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@Test
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@DisplayName("arguments can be customized")
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void argumentsCanBeCustomized() throws NoSuchMethodException {
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var sut = Constructor.create(TestObject.class.getConstructor(String.class, List.class, Map.class));
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// use arg0, because .class files do not store formal parameter names by default
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of(), Map.of("arg0", "customized"), true));
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assertThat(actual.getValue()).isEqualTo("customized");
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}
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@Test
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@DisplayName("using constructor is used for all instances")
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void usingConstructorIsRecursive() throws NoSuchMethodException {
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var sut = Constructor.create(TestObjectWithConstructedField.class.getConstructor(int.class, TestObjectWithGenericConstructor.class));
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of(), Map.of(), true));
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assertThat(actual).isInstanceOf(TestObjectWithConstructedField.class);
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assertThat(actual.getTestObjectWithGenericConstructor().getPrivateField()).isNull();
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assertThat(actual.getNotSetByConstructor()).isNull();
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}
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@Test
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@DisplayName("customized arguments are only used for the top level object (no nested objects)")
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void constructorArgumentsAreUsedOnce() throws NoSuchMethodException {
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var sut = Constructor.create(TestObjectWithConstructedField.class.getConstructor(int.class, TestObjectWithGenericConstructor.class));
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// use arg0, because .class files do not store formal parameter names by default
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of(), Map.of("arg0", 2), true));
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assertThat(actual.getSetByConstructor()).isEqualTo(2);
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}
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@Test
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@DisplayName("customized arguments are used for exclusion, too")
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void ignoredConstructorArgsAreRespected() throws NoSuchMethodException {
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var sut = Constructor.create(TestObjectWithConstructedField.class.getConstructor(int.class, TestObjectWithGenericConstructor.class));
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// use arg0, because .class files do not store formal parameter names by default
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var actual = sut.invoke(new SpecimenFactory(new Context(Configuration.configure())), new CustomizationContext(List.of("arg0"), Map.of(), true));
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assertThat(actual.getSetByConstructor()).isEqualTo(0);
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}
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}

‎src/test/java/com/github/nylle/javafixture/instantiation/PrimitiveTest.java‎

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package com.github.nylle.javafixture.instantiation;
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import com.github.nylle.javafixture.annotations.testcases.TestCase;
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import com.github.nylle.javafixture.annotations.testcases.TestWithCases;
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import org.junit.jupiter.api.Test;
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import static org.assertj.core.api.Assertions.assertThat;
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class PrimitiveTest {
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@Test
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void returnsDefaultBoolean() {
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assertThat(Primitive.defaultValue(boolean.class)).isEqualTo(false);
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}
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@Test
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void returnsDefaultCharacter() {
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assertThat(Primitive.defaultValue(char.class)).isEqualTo('\0');
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}
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@Test
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void returnsDefaultByte() {
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assertThat(Primitive.defaultValue(byte.class)).isEqualTo((byte) 0);
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}
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@TestWithCases
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@TestCase(class1 = short.class)
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@TestCase(class1 = int.class)
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void returnsDefaultInteger(Class<?> type) {
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assertThat(Primitive.defaultValue(type)).isEqualTo(0);
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}
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@Test
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void returnsDefaultLong() {
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assertThat(Primitive.defaultValue(long.class)).isEqualTo(0L);
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}
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@Test
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void returnsDefaultFloat() {
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assertThat(Primitive.defaultValue(float.class)).isEqualTo(0.0f);
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}
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@Test
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void returnsDefaultDouble() {
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assertThat(Primitive.defaultValue(double.class)).isEqualTo(0.0d);
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}
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@TestWithCases
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@TestCase(class1 = Boolean.class, bool2 = true)
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@TestCase(class1 = Character.class, bool2 = true)
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@TestCase(class1 = Byte.class, bool2 = true)
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@TestCase(class1 = Short.class, bool2 = true)
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@TestCase(class1 = Integer.class, bool2 = true)
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@TestCase(class1 = Long.class, bool2 = true)
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@TestCase(class1 = Float.class, bool2 = true)
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@TestCase(class1 = Double.class, bool2 = true)
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@TestCase(class1 = boolean.class, bool2 = false)
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@TestCase(class1 = char.class, bool2 = false)
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@TestCase(class1 = byte.class, bool2 = false)
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@TestCase(class1 = short.class, bool2 = false)
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@TestCase(class1 = int.class, bool2 = false)
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@TestCase(class1 = long.class, bool2 = false)
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@TestCase(class1 = float.class, bool2 = false)
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@TestCase(class1 = double.class, bool2 = false)
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void returnsNullForBoxedPrimitive(Class<?> type, boolean isNull) {
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assertThat(Primitive.defaultValue(type) == null).isEqualTo(isNull);
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}
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}

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