Add tests for the binary search implementation. (#110)

01_introduction_to_algorithms/java/01_binary_search/src/main/BinarySearch.java

@@ -0,0 +1,63 @@
+package main;
+
+public class BinarySearch {
+    public static void main(String[] args) {
+        int[] myList = {87, 21, 45, 93};
+
+        System.out.println(binarySearch(myList, 93));
+        System.out.println(binarySearch(myList, 16));
+    }
+
+    public static int binarySearch(int[] list, int item) {
+        if (isListEmpty(list)) {
+            return -1;
+        }
+
+        int low = 0;
+        int high = list.length - 1;
+
+        while (low <= high) {
+            int mid = (low + high) / 2;
+            int guess = list[mid];
+
+            if (guessEqualsItem(guess, item)) {
+                return mid;
+            } else if (guessGreaterThanItem(guess, item)) {
+                high = mid - 1;
+            } else if(guessLessThanItem(guess, item)) {
+                low = mid + 1;
+            }
+        }
+
+        return -1;
+    }
+
+    public static boolean isListEmpty(int[] myList) {
+        int listSize = myList.length;
+        if (listSize == 0) {
+            return true;
+        }
+        return false;
+    }
+
+    public static boolean guessEqualsItem(int guess, int item) {
+        if (guess != item) {
+            return false;
+        }
+        return true;
+    }
+
+    public static boolean guessGreaterThanItem(int guess, int item) {
+        if (guess < item) {
+            return false;
+        }
+        return true;
+    }
+
+    public static boolean guessLessThanItem(int guess, int item) {
+        if (guess > item) {
+            return false;
+        }
+        return true;
+    }
+}

01_introduction_to_algorithms/java/01_binary_search/src/test/BinarySearchTest.java

@@ -0,0 +1,50 @@
+package test;
+
+import main.BinarySearch;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BinarySearchTest {
+    @Test
+    public void testListIsEmpty() {
+        BinarySearch binarySearch = new BinarySearch();
+        int[] myList = {6, 9};
+        int[] emptyList = {};
+
+        Assert.assertEquals(false, binarySearch.isListEmpty(myList));
+        Assert.assertEquals(true, binarySearch.isListEmpty(emptyList));
+    }
+
+    @Test
+    public void testGuessEqualsItem() {
+        BinarySearch binarySearch = new BinarySearch();
+
+        Assert.assertEquals(true, binarySearch.guessEqualsItem(3, 3));
+        Assert.assertEquals(false, binarySearch.guessEqualsItem(0, 4));
+    }
+
+    @Test
+    public void testGuessIsLessThanItem() {
+        BinarySearch binarySearch = new BinarySearch();
+
+        Assert.assertEquals(true, binarySearch.guessLessThanItem(2, 7));
+        Assert.assertEquals(false, binarySearch.guessLessThanItem(6, 1));
+    }
+
+    @Test
+    public void testGuessGreaterThanItem() {
+        BinarySearch binarySearch = new BinarySearch();
+
+        Assert.assertEquals(true, binarySearch.guessGreaterThanItem(17, 12));
+        Assert.assertEquals(false, binarySearch.guessGreaterThanItem(13, 28));
+    }
+
+    @Test
+    public void testGivenListAndItemReturnIndexOfItem() {
+        BinarySearch binarySearch = new BinarySearch();
+        int[] testList = {1, 3, 5, 7, 9};
+
+        Assert.assertEquals(1, binarySearch.binarySearch(testList, 3));
+        Assert.assertEquals(-1, binarySearch.binarySearch(testList, 77));
+    }
+}