grades = student.getCourseGrades().values();
+ if (grades.contains(Grade.F)) {
+ throw new EnrollmentException(String.format("Student %s has at least 1 failed course", student.getId()));
+ }
+ // process enrollment...
+ return true;
+ }
+
+ public boolean enrollStudent(Student student, String courseCode) {
+ Course course = courseService.getByCode(courseCode);
+ if (course == null) {
+ throw new EnrollmentException("Course not found: " + courseCode);
+ }
+ return enrollStudent(student, course);
+ }
+
+}
diff --git a/testing-modules/instancio/src/main/java/com/baeldung/instancio/util/PrettyToString.java b/testing-modules/instancio/src/main/java/com/baeldung/instancio/util/PrettyToString.java
new file mode 100644
index 0000000000..163f3673c7
--- /dev/null
+++ b/testing-modules/instancio/src/main/java/com/baeldung/instancio/util/PrettyToString.java
@@ -0,0 +1,21 @@
+package com.baeldung.instancio.util;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+
+public class PrettyToString {
+
+ private static final ObjectWriter objectWriter = new ObjectMapper()
+ .registerModules(new JavaTimeModule())
+ .writerWithDefaultPrettyPrinter();
+
+ public static String toPrettyString(Object obj) {
+ try {
+ return objectWriter.writeValueAsString(obj);
+ } catch (JsonProcessingException e) {
+ throw new RuntimeException(e);
+ }
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/basics/CreateStudentUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/basics/CreateStudentUnitTest.java
new file mode 100644
index 0000000000..524c8dbc91
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/basics/CreateStudentUnitTest.java
@@ -0,0 +1,174 @@
+package com.baeldung.instancio.basics;
+
+import com.baeldung.instancio.student.model.Address;
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.Course;
+import com.baeldung.instancio.student.model.Grade;
+import com.baeldung.instancio.student.model.Phone;
+import com.baeldung.instancio.student.model.Student;
+import org.instancio.Instancio;
+import org.instancio.Model;
+import org.instancio.junit.InstancioExtension;
+import org.instancio.junit.InstancioSource;
+import org.instancio.junit.Seed;
+import org.instancio.junit.WithSettings;
+import org.instancio.settings.Keys;
+import org.instancio.settings.Settings;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+
+import java.time.LocalDate;
+import java.time.Year;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.all;
+import static org.instancio.Select.field;
+
+/**
+ * Sample test class using Instancio to generate test objects.
+ *
+ * Note: using {@link InstancioExtension} is optional. The extension adds support for:
+ *
+ * - reporting seed value if a test fails
+ * - {@link Seed} annotation for reproducing failed tests
+ * - {@link WithSettings} for injecting custom settings, if needed
+ */
+@ExtendWith(InstancioExtension.class)
+class CreateStudentUnitTest {
+
+ /**
+ * Common settings to be used by all test methods.
+ */
+ @WithSettings
+ private static final Settings settings = Settings.create()
+ .set(Keys.COLLECTION_MAX_SIZE, 3);
+
+ /**
+ * A {@link Model} is a template for creating objects.
+ * Objects created from a model can be created as is, or customized, if needed.
+ */
+ private static Model studentModel() {
+ return Instancio.of(Student.class)
+ .generate(field(Student::getDateOfBirth), gen -> gen.temporal().localDate().past())
+ .generate(field(Student::getEnrollmentYear), gen -> gen.temporal().year().past())
+ .generate(field(ContactInfo::getEmail), gen -> gen.text().pattern("#a#a#a#a#a#a@example.com"))
+ .generate(field(Phone::getCountryCode), gen -> gen.string().prefix("+").digits().maxLength(2))
+ .withNullable(field(Student::getEmergencyContact))
+ .toModel();
+ }
+
+ private static void assertModelProperties(Student student) {
+ assertThat(student.getDateOfBirth()).isBefore(LocalDate.now());
+ assertThat(student.getEnrollmentYear()).isLessThan(Year.now());
+ assertThat(student.getContactInfo().getEmail()).matches("^[a-zA-Z0-9]+@example.com$");
+ assertThat(student.getContactInfo().getPhones())
+ .extracting(Phone::getCountryCode)
+ .allSatisfy(countryCode -> assertThat(countryCode).matches("^\\+\\d\\d?$"));
+ }
+
+ /**
+ * Generates random Student objects based on the Model.
+ */
+ @Test
+ void whenGivenAModel_thenShouldCreateAStudentBasedOnModel() {
+ Student student = Instancio.create(studentModel());
+
+ assertModelProperties(student);
+ }
+
+ /**
+ * Generate a list of international students based on the Model.
+ */
+ @Test
+ void whenGivenAModel_thenShouldCreateAListOfStudents() {
+ // Given
+ final int numberOfStudents = 100;
+ final List countries = Arrays.asList(
+ "China", "Germany", "India", "Poland", "Romania", "Sweden", "Switzerland");
+
+ // When
+ List studentList = Instancio.ofList(studentModel())
+ .size(numberOfStudents)
+ .generate(field(Address::getCountry), gen -> gen.oneOf(countries))
+ .create();
+
+ // Then
+ assertThat(studentList).hasSize(numberOfStudents)
+ .allSatisfy(CreateStudentUnitTest::assertModelProperties)
+ .extracting(student -> student.getContactInfo().getAddress().getCountry())
+ .allSatisfy(country -> assertThat(country).isIn(countries));
+ }
+
+ /**
+ * Use the Model to create a student with a failed course.
+ * This test also demonstrates how Instancio can provide
+ * arguments to parameterized tests.
+ *
+ * @param failedCourse provided by Instancio
+ */
+ @InstancioSource
+ @ParameterizedTest
+ void whenGivenFailingGrade_thenStudentShouldHaveAFailedCourse(final Course failedCourse) {
+ // Given
+ final Model model = studentModel();
+ final Grade failingGrade = Grade.F;
+
+ // When
+ Student student = Instancio.of(model)
+ .generate(field(Student::getCourseGrades), gen -> gen.map().with(failedCourse, failingGrade))
+ .create();
+
+ // Then
+ Map courseGrades = student.getCourseGrades();
+ assertModelProperties(student);
+ assertThat(courseGrades).containsEntry(failedCourse, failingGrade);
+ }
+
+ /**
+ * Generate a student with only Grades A and/or B.
+ */
+ @Test
+ void whenGivenGoodGrades_thenCreatedStudentShouldHaveExpectedGrades() {
+ // Given
+ final int numOfCourses = 10;
+ final Grade[] grades = {Grade.A, Grade.B};
+
+ // When
+ Student student = Instancio.of(studentModel())
+ .generate(all(Grade.class), gen -> gen.oneOf(grades))
+ .generate(field(Student::getCourseGrades), gen -> gen.map().size(numOfCourses))
+ .create();
+
+ // Then
+ Map courseGrades = student.getCourseGrades();
+ assertModelProperties(student);
+ assertThat(courseGrades.values())
+ .hasSize(numOfCourses)
+ .containsAnyOf(grades)
+ .doesNotContain(Grade.C, Grade.D, Grade.F);
+ }
+
+ /**
+ * Generate String fields prefixed with the field's name.
+ */
+ @Test
+ void whenGivenCustomSettings_thenStudentShouldBeCreatedUsingTheSettings() {
+ // Given
+ Settings customSettings = Settings.create()
+ .set(Keys.STRING_FIELD_PREFIX_ENABLED, true);
+
+ // When
+ Student student = Instancio.of(studentModel())
+ .withSettings(customSettings)
+ .create();
+
+ // Then
+ assertThat(student.getFirstName()).startsWith("firstName_");
+ assertThat(student.getLastName()).startsWith("lastName_");
+ assertThat(student.getContactInfo().getAddress().getCity()).startsWith("city_");
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/generators/UsingCustomGeneratorUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/generators/UsingCustomGeneratorUnitTest.java
new file mode 100644
index 0000000000..8e5643baec
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/generators/UsingCustomGeneratorUnitTest.java
@@ -0,0 +1,57 @@
+package com.baeldung.instancio.generators;
+
+import com.baeldung.instancio.student.model.Address;
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.Phone;
+import com.baeldung.instancio.student.model.Student;
+import org.instancio.Instancio;
+import org.instancio.Random;
+import org.instancio.generator.AfterGenerate;
+import org.instancio.generator.Generator;
+import org.instancio.generator.Hints;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.all;
+import static org.instancio.Select.field;
+
+class UsingCustomGeneratorUnitTest {
+ private static final String ARGENTINA = "Argentina";
+ private static final int PHONES_SIZE = 5;
+
+ private static final Generator ADDRESS_GENERATOR = new Generator() {
+ @Override
+ public Address generate(final Random random) {
+ Address address = new Address();
+ address.setCountry(ARGENTINA);
+ return address;
+ }
+
+ @Override
+ public Hints hints() {
+ // The hint telling the engine to populate any field that has a null value
+ return Hints.afterGenerate(AfterGenerate.POPULATE_NULLS);
+ }
+ };
+
+ @Test
+ void whenGivenAGenerator_objectShouldBeCreatedUsingCustomGenerator() {
+ Student student = Instancio.of(Student.class)
+ .supply(all(Address.class), ADDRESS_GENERATOR)
+ .generate(field(ContactInfo::getPhones), gen -> gen.collection().size(PHONES_SIZE))
+ .create();
+
+ ContactInfo contactInfo = student.getContactInfo();
+ Address address = contactInfo.getAddress();
+ List phones = contactInfo.getPhones();
+
+ assertThat(phones).hasSize(PHONES_SIZE);
+ assertThat(address.getCountry()).isEqualTo(ARGENTINA);
+ // null fields were populated with random values
+ assertThat(address.getStreet()).isNotNull();
+ assertThat(address.getCity()).isNotNull();
+ }
+
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/generics/CreatingGenericTypesUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/generics/CreatingGenericTypesUnitTest.java
new file mode 100644
index 0000000000..4ed22abeaf
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/generics/CreatingGenericTypesUnitTest.java
@@ -0,0 +1,100 @@
+package com.baeldung.instancio.generics;
+
+import com.baeldung.instancio.student.model.Address;
+import org.instancio.Instancio;
+import org.instancio.TypeToken;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.allLongs;
+import static org.instancio.Select.allStrings;
+
+/**
+ * Examples of creating generic types using {@link TypeToken}.
+ */
+class CreatingGenericTypesUnitTest {
+
+
+ @Test
+ void whenGivenTypeToken_shouldCreateItem() {
+ Item item = Instancio.create(new TypeToken>() {});
+
+ assertThat(item.getValue()).isNotBlank();
+ }
+
+ @Test
+ void whenGivenTypeToken_shouldCreateCustomizedItem() {
+ Pair pair = Instancio.of(new TypeToken>() {})
+ .generate(allStrings(), gen -> gen.oneOf("foo", "bar"))
+ .generate(allLongs(), gen -> gen.longs().range(5L, 10L))
+ .create();
+
+ assertThat(pair.getLeft()).isIn("foo", "bar");
+ assertThat(pair.getRight()).isBetween(5L, 10L);
+ }
+
+ @Test
+ void whenGivenTypeToken_shouldCreateTriplet() {
+ Triplet triplet = Instancio.create(new TypeToken>() {});
+
+ assertThat(triplet.getLeft()).isNotBlank();
+ assertThat(triplet.getMiddle()).isNotNull();
+ assertThat(triplet.getRight()).isNotNull();
+ }
+
+ @Test
+ void whenGivenTypeToken_shouldCreateCollection() {
+ List list = Instancio.create(new TypeToken>() {});
+
+ assertThat(list).isNotEmpty().doesNotContainNull();
+ }
+
+ @Test
+ void whenGivenTypeToken_shouldCreateMap() {
+ Map map = Instancio.create(new TypeToken>() {});
+
+ assertThat(map).isNotEmpty();
+ }
+
+ /**
+ * Using type token to create more complex generic objects.
+ */
+ @Test
+ void whenGivenTypeTokenWithNestGenerics_shouldCreateAnInstanceOfSpecifiedType() {
+ List>> list = Instancio.create(
+ new TypeToken>>>() {});
+
+ assertThat(list)
+ .isNotEmpty()
+ .allSatisfy(triplet -> {
+ assertThat(triplet.getLeft()).isInstanceOf(Integer.class);
+ assertThat(triplet.getMiddle()).isInstanceOf(LocalDate.class);
+ assertThat(triplet.getRight())
+ .isInstanceOf(Item.class)
+ .satisfies(item -> assertThat(item.getValue()).isNotBlank());
+ });
+
+ // Sample output
+ list.forEach(System.out::println);
+ }
+
+
+ /**
+ * Alternative way to create generic objects is using 'withTypeParameters'.
+ * However, this approach generates an "unchecked assignment" warning.
+ */
+ @Test
+ @SuppressWarnings("unchecked")
+ void whenGivenClassWithTypeParameters_shouldCreateGenericType() {
+ Map map = Instancio.of(Map.class)
+ .withTypeParameters(UUID.class, Address.class)
+ .create();
+
+ assertThat(map).isNotEmpty();
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/mockito/InstancioWithMockitoUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/mockito/InstancioWithMockitoUnitTest.java
new file mode 100644
index 0000000000..1382589a84
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/mockito/InstancioWithMockitoUnitTest.java
@@ -0,0 +1,45 @@
+package com.baeldung.instancio.mockito;
+
+import com.baeldung.instancio.student.model.Course;
+import com.baeldung.instancio.student.model.Grade;
+import com.baeldung.instancio.student.model.Student;
+import com.baeldung.instancio.student.service.CourseService;
+import com.baeldung.instancio.student.service.EnrollmentService;
+import org.instancio.Instancio;
+import org.instancio.junit.InstancioExtension;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.all;
+import static org.mockito.Mockito.when;
+
+@ExtendWith({MockitoExtension.class, InstancioExtension.class})
+class InstancioWithMockitoUnitTest {
+
+ @Mock
+ private CourseService courseService;
+
+ @InjectMocks
+ private EnrollmentService enrollmentService;
+
+ @Test
+ void givenStudentWithoutGradeF_thenShouldEnrollStudentInCourse() {
+ // Given
+ Student student = Instancio.of(Student.class)
+ .generate(all(Grade.class), gen -> gen.enumOf(Grade.class).excluding(Grade.F))
+ .create();
+
+ Course course = Instancio.create(Course.class);
+ when(courseService.getByCode(course.getCode())).thenReturn(course);
+
+ // When
+ boolean isEnrolled = enrollmentService.enrollStudent(student, course.getCode());
+
+ // Then
+ assertThat(isEnrolled).isTrue();
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/reproducing/ReproducingTestFailureUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/reproducing/ReproducingTestFailureUnitTest.java
new file mode 100644
index 0000000000..0d6c8cfa9a
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/reproducing/ReproducingTestFailureUnitTest.java
@@ -0,0 +1,60 @@
+package com.baeldung.instancio.reproducing;
+
+import com.baeldung.instancio.student.model.Course;
+import com.baeldung.instancio.student.model.Student;
+import com.baeldung.instancio.student.service.EnrollmentService;
+import org.instancio.Instancio;
+import org.instancio.junit.InstancioExtension;
+import org.instancio.junit.Seed;
+import org.instancio.junit.WithSettings;
+import org.instancio.settings.Keys;
+import org.instancio.settings.Settings;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(InstancioExtension.class)
+class ReproducingTestFailureUnitTest {
+
+ @WithSettings
+ private static final Settings settings = Settings.create()
+ .set(Keys.COLLECTION_MIN_SIZE, 50)
+ .set(Keys.COLLECTION_MAX_SIZE, 100)
+ .lock();
+
+ private final EnrollmentService enrollmentService = new EnrollmentService();
+
+ /**
+ * This test fails because the {@code enrollInCourse()} method
+ * throws an exception if the student has at least one grade F.
+ *
+ * Sample error message generated by {@link InstancioExtension}:
+ *
+ *
+ * timestamp = 2023-01-24T13:50:12.436704221, Instancio = Test method 'enrollStudent' failed with seed: 1234
+ *
+ *
+ * Using the reported seed value we can reproduce the test failure.
+ */
+ @Test
+ @Seed(1234)
+ @Disabled("This test fails on purpose to demonstrate failure reporting by InstancioExtension")
+ void whenGivenNoFailingGrades_thenShouldEnrollStudentInCourse() {
+ // Given
+ Course course = Instancio.create(Course.class);
+ Student student = Instancio.of(Student.class)
+ // The test can be fixed by uncommenting the line below:
+ //.generate(all(Grade.class), gen -> gen.enumOf(Grade.class).excluding(Grade.F))
+ .create();
+
+ System.out.println(student); // same data generated on each run
+
+ // When
+ boolean isEnrolled = enrollmentService.enrollStudent(student, course);
+
+ // Then
+ assertThat(isEnrolled).isTrue();
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorScopesUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorScopesUnitTest.java
new file mode 100644
index 0000000000..683b510f0c
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorScopesUnitTest.java
@@ -0,0 +1,76 @@
+package com.baeldung.instancio.selectors;
+
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.EmergencyContact;
+import com.baeldung.instancio.student.model.Phone;
+import com.baeldung.instancio.student.model.Student;
+import org.instancio.Instancio;
+import org.instancio.Scope;
+import org.instancio.Select;
+import org.instancio.TargetSelector;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.allStrings;
+import static org.instancio.Select.scope;
+
+/**
+ * Examples of various selector {@link Scope}.
+ * Scopes allow narrowing down selector targets.
+ */
+class SelectorScopesUnitTest {
+
+ /**
+ * Prefix all String fields in Phone class with "phone_".
+ */
+ @Test
+ void whenGivenClassScope_shouldSelectTargetsWithinClass() {
+ // Given
+ final String prefix = "phone_";
+ final Scope phoneClass = scope(Phone.class);
+
+ // When
+ Student student = Instancio.of(Student.class)
+ .generate(allStrings().within(phoneClass), gen -> gen.string().prefix(prefix))
+ .create();
+
+ // Then
+
+ // matches phone numbers
+ Phone emergencyContactPhone = student.getEmergencyContact().getPhone();
+ assertThat(emergencyContactPhone.getCountryCode()).startsWith(prefix);
+ assertThat(emergencyContactPhone.getNumber()).startsWith(prefix);
+ assertThat(student.getContactInfo().getPhones()).allSatisfy(phone -> {
+ assertThat(phone.getCountryCode()).startsWith(prefix);
+ assertThat(phone.getNumber()).startsWith(prefix);
+ });
+
+ // does not match other fields
+ assertThat(student.getContactInfo().getAddress().getCity()).doesNotStartWith(prefix);
+ }
+
+ /**
+ * Using scope to set student's and their emergency contact's
+ * phone number to different values.
+ */
+ @Test
+ void whenGivenFieldScope_shouldSelectTargetsWithinField() {
+ // Given
+ TargetSelector studentPhone = Select.field(Phone::getNumber).within(scope(ContactInfo.class));
+ TargetSelector emergencyPhone = Select.field(Phone::getNumber).within(scope(EmergencyContact.class));
+
+ // When
+ Student student = Instancio.of(Student.class)
+ .set(studentPhone, "student")
+ .set(emergencyPhone, "emergency")
+ .create();
+
+ // Then
+ assertThat(student.getContactInfo().getPhones())
+ .isNotEmpty()
+ .allSatisfy(phone -> assertThat(phone.getNumber()).isEqualTo("student"));
+
+ assertThat(student.getEmergencyContact().getPhone().getNumber())
+ .isEqualTo("emergency");
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorsUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorsUnitTest.java
new file mode 100644
index 0000000000..fe6b9cc3f4
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/selectors/SelectorsUnitTest.java
@@ -0,0 +1,104 @@
+package com.baeldung.instancio.selectors;
+
+import com.baeldung.instancio.student.model.Address;
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.Phone;
+import com.baeldung.instancio.student.model.Student;
+import org.instancio.FieldSelectorBuilder;
+import org.instancio.Instancio;
+import org.instancio.Select;
+import org.instancio.Selector;
+import org.instancio.SelectorGroup;
+import org.instancio.TargetSelector;
+import org.junit.jupiter.api.Test;
+
+import java.util.Collection;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.all;
+import static org.instancio.Select.field;
+import static org.instancio.Select.fields;
+import static org.instancio.Select.types;
+
+/**
+ * Examples of various types of selectors provided by the {@link Select} class.
+ */
+class SelectorsUnitTest {
+
+ @Test
+ void whenGivenFieldSelector_shouldCustomizeSelectedField() {
+ Address address = Instancio.of(Address.class)
+ .set(field(Address::getCity), "London")
+ .set(field(Address.class, "country"), "UK")
+ .create();
+
+ assertThat(address.getCity()).isEqualTo("London");
+ assertThat(address.getCountry()).isEqualTo("UK");
+ }
+
+ @Test
+ void whenGivenClassSelector_shouldCustomizeSelectedClass() {
+ // Given
+ final Selector allStrings = all(String.class);
+ final String prefix = "test_";
+
+ // When
+ Address address = Instancio.of(Address.class)
+ .generate(allStrings, gen -> gen.string().prefix(prefix))
+ .create();
+
+ // Then
+ assertThat(address.getCity()).startsWith(prefix);
+ assertThat(address.getCountry()).startsWith(prefix);
+ }
+
+ @Test
+ void whenGivenPredicateFieldSelector_shouldCustomizeMatchingFields() {
+ // Given: regie matching 'city' and 'country' fields
+ final FieldSelectorBuilder fieldsMatchingRegex = fields().matching("c.*y");
+
+ // When
+ Address address = Instancio.of(Address.class)
+ .ignore(fieldsMatchingRegex)
+ .create();
+
+ // Then
+ assertThat(address.getCity()).isNull();
+ assertThat(address.getCountry()).isNull();
+ assertThat(address.getStreet()).isNotBlank();
+ }
+
+ @Test
+ void whenGivenPredicateClassSelector_shouldCustomizeMatchingClasses() {
+ // Given
+ final TargetSelector allTypesOfCollections = types().of(Collection.class);
+ final int size = 3;
+
+ // When
+ ContactInfo contactInfo = Instancio.of(ContactInfo.class)
+ .generate(allTypesOfCollections, gen -> gen.collection().size(size))
+ .create();
+
+ // Then
+ List phones = contactInfo.getPhones();
+ assertThat(phones).hasSize(size);
+ }
+
+ @Test
+ void whenGivenSelectorGroup_shouldCustomizeSelectedFields() {
+ // Given
+ SelectorGroup ignoredFields = all(
+ field(Student::getId),
+ field(Student::getDateOfBirth));
+
+ // When
+ Student student = Instancio.of(Student.class)
+ .ignore(ignoredFields)
+ .create();
+
+ // Then
+ assertThat(student.getId()).isNull();
+ assertThat(student.getDateOfBirth()).isNull();
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/CustomSettingsUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/CustomSettingsUnitTest.java
new file mode 100644
index 0000000000..b9b8b4ac6d
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/CustomSettingsUnitTest.java
@@ -0,0 +1,67 @@
+package com.baeldung.instancio.settings;
+
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.Phone;
+import org.instancio.Instancio;
+import org.instancio.junit.InstancioExtension;
+import org.instancio.junit.WithSettings;
+import org.instancio.settings.Keys;
+import org.instancio.settings.Settings;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * {@link InstancioExtension} allows injecting custom settings
+ * using the {@link WithSettings} annotation.
+ */
+@ExtendWith(InstancioExtension.class)
+class CustomSettingsUnitTest {
+
+ private static final int MIN_SIZE = 0;
+ private static final int MAX_SIZE = 3;
+
+ /**
+ * Common settings to be used by all test methods.
+ */
+ @WithSettings
+ private static final Settings settings = Settings.create()
+ .set(Keys.COLLECTION_MIN_SIZE, MIN_SIZE)
+ .set(Keys.COLLECTION_MAX_SIZE, MAX_SIZE)
+ .lock();
+
+
+ @Test
+ void whenGivenInjectedSettings_shouldUseCustomSettings() {
+ ContactInfo info = Instancio.create(ContactInfo.class);
+
+ List phones = info.getPhones();
+ assertThat(phones).hasSizeBetween(MIN_SIZE, MAX_SIZE);
+ }
+
+ @Test
+ void whenSettingsOverridden_shouldUseTheOverrides() {
+ // Given
+ final int collectionSize = 50;
+ Settings additionalSettings = Settings.create()
+ .set(Keys.STRING_FIELD_PREFIX_ENABLED, true)
+ .set(Keys.COLLECTION_MIN_SIZE, collectionSize)
+ .set(Keys.COLLECTION_MAX_SIZE, collectionSize);
+
+ // When
+ ContactInfo info = Instancio.of(ContactInfo.class)
+ .withSettings(additionalSettings)
+ .create();
+
+ // Then
+ assertThat(info.getPhones())
+ .hasSize(collectionSize)
+ .allSatisfy(phone -> {
+ assertThat(phone.getCountryCode()).startsWith("countryCode_");
+ assertThat(phone.getNumber()).startsWith("number_");
+ });
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/UsingInstancioPropertiesUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/UsingInstancioPropertiesUnitTest.java
new file mode 100644
index 0000000000..6a14d8dc88
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/settings/UsingInstancioPropertiesUnitTest.java
@@ -0,0 +1,50 @@
+package com.baeldung.instancio.settings;
+
+import org.instancio.Instancio;
+import org.instancio.settings.Keys;
+import org.instancio.settings.Settings;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class UsingInstancioPropertiesUnitTest {
+
+ /**
+ * Instancio automatically loads {@code instancio.properties} file,
+ * if it's present, from the root of the classpath.
+ *
+ * Float range was overridden to [0, 100].
+ * See: {@code src/test/resources/instancio.properties}
+ */
+ @Test
+ void whenInstancioPropertiesAreOnClasspath_shouldUseConfiguredProperties() {
+ Set floats = Instancio.ofSet(Float.class).create();
+
+ assertThat(floats)
+ .isNotEmpty()
+ .allSatisfy(f -> assertThat(f).isBetween(0f, 100f));
+ }
+
+ /**
+ * We can override global configuration using {@link Settings}.
+ */
+ @Test
+ void whenCustomSettingsAreProvided_shouldOverrideInstancioProperties() {
+ // Given
+ Settings settings = Settings.create()
+ .set(Keys.FLOAT_MIN, 100f)
+ .set(Keys.FLOAT_MAX, 200f);
+
+ // When
+ Set floats = Instancio.ofSet(Float.class)
+ .withSettings(settings)
+ .create();
+
+ // Then
+ assertThat(floats)
+ .isNotEmpty()
+ .allSatisfy(f -> assertThat(f).isBetween(100f, 200f));
+ }
+}
diff --git a/testing-modules/instancio/src/test/java/com/baeldung/instancio/subtype/SubtypeUnitTest.java b/testing-modules/instancio/src/test/java/com/baeldung/instancio/subtype/SubtypeUnitTest.java
new file mode 100644
index 0000000000..7bbfaa497f
--- /dev/null
+++ b/testing-modules/instancio/src/test/java/com/baeldung/instancio/subtype/SubtypeUnitTest.java
@@ -0,0 +1,54 @@
+package com.baeldung.instancio.subtype;
+
+import com.baeldung.instancio.abstracttype.AbstractItem;
+import com.baeldung.instancio.generics.Item;
+import com.baeldung.instancio.student.model.ContactInfo;
+import com.baeldung.instancio.student.model.Student;
+import org.instancio.Instancio;
+import org.instancio.TypeToken;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDateTime;
+import java.util.LinkedList;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.instancio.Select.all;
+import static org.instancio.Select.field;
+
+/**
+ * Using {@code subtype()} method we can specify a specific implementation
+ * class for an abstract type, or a specialized subclass for a concrete class.
+ */
+class SubtypeUnitTest {
+
+ @Test
+ void whenGivenCollectionSubtype_shouldUseSpecifiedCollectionClass() {
+ // Given
+ final Class subtype = LinkedList.class;
+
+ // When
+ Student student = Instancio.of(Student.class)
+ .subtype(field(ContactInfo::getPhones), subtype)
+ .create();
+
+ // Then
+ assertThat(student.getContactInfo().getPhones())
+ .isNotEmpty()
+ .isExactlyInstanceOf(subtype);
+ }
+
+ @Test
+ void whenGivenSubtypeForGenericAbstractType_shouldUseSpecifiedConcreteClass() {
+ // Given
+ final Class subtype = Item.class;
+
+ // When
+ AbstractItem abstractItem = Instancio.of(new TypeToken>() {})
+ .subtype(all(AbstractItem.class), subtype)
+ .create();
+
+ // Then
+ assertThat(abstractItem).isExactlyInstanceOf(subtype);
+ assertThat(abstractItem.getValue()).isNotNull();
+ }
+}
diff --git a/testing-modules/instancio/src/test/resources/instancio.properties b/testing-modules/instancio/src/test/resources/instancio.properties
new file mode 100644
index 0000000000..a314af0a3f
--- /dev/null
+++ b/testing-modules/instancio/src/test/resources/instancio.properties
@@ -0,0 +1,2 @@
+float.min=1
+float.max=100
diff --git a/testing-modules/pom.xml b/testing-modules/pom.xml
index f237d2d6fc..64546b5064 100644
--- a/testing-modules/pom.xml
+++ b/testing-modules/pom.xml
@@ -22,6 +22,7 @@
gatling
groovy-spock
hamcrest
+ instancio
junit-4
junit-5-advanced
junit-5-basics
diff --git a/testing-modules/testing-libraries/pom.xml b/testing-modules/testing-libraries/pom.xml
index f9443fa792..b7c9b8c0bd 100644
--- a/testing-modules/testing-libraries/pom.xml
+++ b/testing-modules/testing-libraries/pom.xml
@@ -90,6 +90,11 @@
+
+ org.codehaus.mojo
+ findbugs-maven-plugin
+ ${findbugs-plugin.version}
+
@@ -111,8 +116,9 @@
4.8.0
3.0.0
1.19.0
- 1.0.0
+ 1.2.1
2.4.3
+ 3.0.5
\ No newline at end of file