Added test for MinimumWindowSubstring

Author: jaimin45-art

src/test/java/com/thealgorithms/strings/MinimumWindowSubstringTest.java

@@ -0,0 +1,27 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+public class MinimumWindowSubstringTest {
+
+    @Test
+    public void testExample1() {
+        assertEquals("BANC", MinimumWindowSubstring.minWindow("ADOBECODEBANC", "ABC"));
+    }
+
+    @Test
+    public void testExample2() {
+        assertEquals("", MinimumWindowSubstring.minWindow("A", "AA"));
+    }
+
+    @Test
+    public void testExample3() {
+        assertEquals("a", MinimumWindowSubstring.minWindow("a", "a"));
+    }
+
+    @Test
+    public void testExample4() {
+        assertEquals("t stri", MinimumWindowSubstring.minWindow("test string", "tist"));
+    }
+}