testing: improve test coverage RangeInSortedArrayTest (#6395)

* testing: improve test coverage RangeInSortedArrayTest

* style: fix formatting checkstyle

---------

Co-authored-by: Deniz Altunkapan <[email protected]>

Author: alxkm

src/test/java/com/thealgorithms/misc/RangeInSortedArrayTest.java

@@ -32,4 +32,26 @@ private static Stream<Arguments> provideGetCountLessThanTestCases() {
         return Stream.of(Arguments.of(new int[] {1, 2, 3, 3, 4, 5}, 3, 4, "Count of elements less than existing key"), Arguments.of(new int[] {1, 2, 3, 3, 4, 5}, 4, 5, "Count of elements less than non-existing key"), Arguments.of(new int[] {1, 2, 2, 3}, 5, 4, "Count with all smaller elements"),
             Arguments.of(new int[] {2, 3, 4, 5}, 1, 0, "Count with no smaller elements"), Arguments.of(new int[] {}, 1, 0, "Count in empty array"));
     }
+
+    @ParameterizedTest(name = "Edge case {index}: {3}")
+    @MethodSource("provideEdgeCasesForSortedRange")
+    void testSortedRangeEdgeCases(int[] nums, int key, int[] expectedRange, String description) {
+        assertArrayEquals(expectedRange, RangeInSortedArray.sortedRange(nums, key), description);
+    }
+
+    private static Stream<Arguments> provideEdgeCasesForSortedRange() {
+        return Stream.of(Arguments.of(new int[] {5, 5, 5, 5, 5}, 5, new int[] {0, 4}, "All elements same as key"), Arguments.of(new int[] {1, 2, 3, 4, 5}, 1, new int[] {0, 0}, "Key is first element"), Arguments.of(new int[] {1, 2, 3, 4, 5}, 5, new int[] {4, 4}, "Key is last element"),
+            Arguments.of(new int[] {1, 2, 3, 4, 5}, 0, new int[] {-1, -1}, "Key less than all elements"), Arguments.of(new int[] {1, 2, 3, 4, 5}, 6, new int[] {-1, -1}, "Key greater than all elements"),
+            Arguments.of(new int[] {1, 2, 2, 2, 3, 3, 3, 4}, 3, new int[] {4, 6}, "Multiple occurrences spread"), Arguments.of(new int[] {2}, 2, new int[] {0, 0}, "Single element array key exists"), Arguments.of(new int[] {2}, 3, new int[] {-1, -1}, "Single element array key missing"));
+    }
+
+    @ParameterizedTest(name = "Edge case {index}: {3}")
+    @MethodSource("provideEdgeCasesForGetCountLessThan")
+    void testGetCountLessThanEdgeCases(int[] nums, int key, int expectedCount, String description) {
+        assertEquals(expectedCount, RangeInSortedArray.getCountLessThan(nums, key), description);
+    }
+
+    private static Stream<Arguments> provideEdgeCasesForGetCountLessThan() {
+        return Stream.of(Arguments.of(new int[] {1, 2, 3, 4, 5}, 0, 0, "Key less than all elements"), Arguments.of(new int[] {1, 2, 3, 4, 5}, 6, 5, "Key greater than all elements"), Arguments.of(new int[] {1}, 0, 0, "Single element greater than key"));
+    }
 }