Added test on ThrowingSupplier

junit/junit5/functional-interfaces/src/test/java/io/reflectoring/functional/ThrowingSupplierTest.java

@@ -0,0 +1,81 @@
+package io.reflectoring.functional;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTimeout;
+import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.ThrowingSupplier;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.opentest4j.AssertionFailedError;
+
+public class ThrowingSupplierTest {
+  private final List<Long> numbers = Arrays.asList(100L, 200L, 50L, 300L);
+  private final Consumer<List<Long>> checkSorting =
+      list -> assertEquals(List.of(50L, 100L, 200L, 300L), list);
+
+  ThrowingSupplier<List<Long>> sorter =
+      () -> {
+        if (numbers == null || numbers.isEmpty() || numbers.contains(null)) {
+          throw new ValidationException("Invalid input");
+        }
+        TimeUnit.SECONDS.sleep(2);
+        return numbers.stream().sorted().toList();
+      };
+
+  @ParameterizedTest
+  @CsvSource({"25.0d,5.0d", "36.0d,6.0d", "49.0d,7.0d"})
+  void testDoesNotThrowWithSupplier(double input, double expected) {
+    ThrowingSupplier<Double> findSquareRoot =
+        () -> {
+          if (input < 0) {
+            throw new ValidationException("Invalid input");
+          }
+          return Math.sqrt(input);
+        };
+    assertEquals(expected, assertDoesNotThrow(findSquareRoot));
+  }
+
+  @Test
+  void testAssertTimeoutWithSupplier() {
+    // slow execution
+    assertThrows(AssertionFailedError.class, () -> assertTimeout(Duration.ofSeconds(1), sorter));
+
+    // fast execution
+    assertDoesNotThrow(
+        () -> {
+          List<Long> result = assertTimeout(Duration.ofSeconds(5), sorter);
+          checkSorting.accept(result);
+        });
+
+    // reset the number list and verify if the supplier validates it
+    Collections.fill(numbers, null);
+
+    ValidationException exception =
+        assertThrows(ValidationException.class, () -> assertTimeout(Duration.ofSeconds(1), sorter));
+    assertEquals("Invalid input", exception.getMessage());
+  }
+
+  @Test
+  void testAssertTimeoutPreemptivelyWithSupplier() {
+    // slow execution
+    assertThrows(
+        AssertionFailedError.class, () -> assertTimeoutPreemptively(Duration.ofSeconds(1), sorter));
+
+    // fast execution
+    assertDoesNotThrow(
+        () -> {
+          List<Long> result = assertTimeoutPreemptively(Duration.ofSeconds(5), sorter);
+          checkSorting.accept(result);
+        });
+  }
+}