Add unit tests for suffix tree

src/_DataStructures_/Trees/SuffixTree/SuffixTree.test.js

@@ -0,0 +1,43 @@
+const SuffixTree = require('.');
+
+describe('Data Structure : Suffix Tree', () => {
+  it('Should be class', () => {
+    expect(typeof SuffixTree.prototype.constructor).toEqual('function');
+  });
+
+  it('Should correctly construct Suffix Tree from string', () => {
+    const banana = new SuffixTree('banana');
+    banana.constructSuffixTree();
+
+    expect(banana.findSubstring('banana')).toBe(0);
+    expect(banana.findSubstring('nana')).toBe(2);
+    expect(banana.findSubstring('na')).toBe(4);
+    expect(banana.findSubstring('an')).toBe(-1);
+
+    const suffix = new SuffixTree('suffix');
+    suffix.constructSuffixTree();
+
+    expect(suffix.findSubstring('fix')).toBe(3);
+
+    const kebab = new SuffixTree('kebab');
+    kebab.constructSuffixTree();
+
+    expect(kebab.findSubstring('horse')).toBe(-1);
+
+    const mississippi = new SuffixTree('mississippi');
+    mississippi.constructSuffixTree();
+
+    expect(mississippi.findSubstring('ssippi')).toBe(5);
+    expect(mississippi.findSubstring('ppi')).toBe(8);
+    expect(mississippi.findSubstring('mis')).toBe(-1);
+    expect(mississippi.findSubstring('pi')).toBe(9);
+
+    const linkedList = new SuffixTree('aaaaaaaaaaa');
+    linkedList.constructSuffixTree();
+
+    expect(linkedList.findSubstring('a')).toBe(10);
+    expect(linkedList.findSubstring('aaa')).toBe(8);
+    expect(linkedList.findSubstring('b')).toBe(-1);
+    expect(linkedList.findSubstring('')).toBe(-1);
+  });
+});