diff --git a/core-java-modules/core-java-arrays-operations-basic-2/src/test/java/com/baeldung/array/flatarray/FlatArrayUnitTest.java b/core-java-modules/core-java-arrays-operations-basic-2/src/test/java/com/baeldung/array/flatarray/FlatArrayUnitTest.java
new file mode 100644
index 0000000000..5d67c68a37
--- /dev/null
+++ b/core-java-modules/core-java-arrays-operations-basic-2/src/test/java/com/baeldung/array/flatarray/FlatArrayUnitTest.java
@@ -0,0 +1,130 @@
+package com.baeldung.array.flatarray;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class FlatArrayUnitTest {
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithStream_thenGetCorrectResult(int[][] initialArray,
+      int[] expected) {
+        int[] actual = Arrays.stream(initialArray).flatMapToInt(Arrays::stream).toArray();
+        assertThat(actual).containsExactly(expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithForLoopAndAdditionalList_thenGetCorrectResult(int[][] initialArray,
+      int[] intArray) {
+        List<Integer> expected = Arrays.stream(intArray).boxed().collect(Collectors.toList());
+        List<Integer> actual = new ArrayList<>();
+        for (int[] numbers : initialArray) {
+            for (int number : numbers) {
+                actual.add(number);
+            }
+        }
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithForLoopAndLists_thenGetCorrectResult(int[][] initialArray,
+      int[] intArray) {
+        List<Integer> expected = Arrays.stream(intArray).boxed().collect(Collectors.toList());
+        List<Integer> actual = new ArrayList<>();
+        for (int[] numbers : initialArray) {
+            List<Integer> listOfNumbers = Arrays.stream(numbers).boxed().collect(Collectors.toList());
+            actual.addAll(listOfNumbers);
+        }
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithArrayCopy_thenGetCorrectResult(int[][] initialArray,
+      int[] expected) {
+        int[] actual = new int[]{};
+        int position = 0;
+        for (int[] numbers : initialArray) {
+            if (actual.length < position + numbers.length) {
+                int[] newArray = new int[actual.length + numbers.length];
+                System.arraycopy(actual, 0, newArray, 0, actual.length);
+                actual = newArray;
+            }
+            System.arraycopy(numbers, 0, actual, position, numbers.length);
+            position += numbers.length;
+        }
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithArrayCopyAndTotalNumberOfElements_thenGetCorrectResult(int[][] initialArray,
+      int[] expected) {
+        int totalNumberOfElements = 0;
+        for (int[] numbers : initialArray) {
+            totalNumberOfElements += numbers.length;
+        }
+        int[] actual = new int[totalNumberOfElements];
+        int position = 0;
+        for (int[] numbers : initialArray) {
+            System.arraycopy(numbers, 0, actual, position, numbers.length);
+            position += numbers.length;
+        }
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("arrayProvider")
+    void giveTwoDimensionalArray_whenFlatWithForLoopAndTotalNumberOfElements_thenGetCorrectResult(int[][] initialArray,
+      int[] expected) {
+        int totalNumberOfElements = 0;
+        for (int[] numbers : initialArray) {
+            totalNumberOfElements += numbers.length;
+        }
+        int[] actual = new int[totalNumberOfElements];
+        int position = 0;
+        for (int[] numbers : initialArray) {
+            for (int number : numbers) {
+                actual[position] = number;
+                ++position;
+            }
+        }
+        assertThat(actual).isEqualTo(expected);
+    }
+
+
+    static Stream<Arguments> arrayProvider() {
+        return Stream.of(
+          Arguments.of(
+            new int[][]{
+              {805, 902, 259, 162, 775},
+              {278, 216, 0, 72, 663},
+              {185, 390, 537, 909, 918},
+              {150, 782, 282, 482, 401},
+              {244, 685, 643, 364, 307},
+              {483, 939, 750, 190, 424},
+              {44, 160, 290, 963, 881}
+            },
+            new int[]{
+              805, 902, 259, 162, 775,
+              278, 216, 0, 72, 663,
+              185, 390, 537, 909, 918,
+              150, 782, 282, 482, 401,
+              244, 685, 643, 364, 307,
+              483, 939, 750, 190, 424,
+              44, 160, 290, 963, 881
+            }
+          )
+        );
+    }
+}