Added tests for Strings algorithms (#390)

* test: added tests for check anagram function

String/PatternMatching.test.js

@@ -0,0 +1,26 @@
+import { checkIfPatternExists } from './PatternMatching'
+describe('checkIfPatternExists', () => {
+  it('expects to find a pattern with correct input', () => {
+    const text = 'AABAACAADAABAAAABAA'
+    const pattern = 'AABA'
+    const SUT = checkIfPatternExists(text.toLowerCase(), pattern.toLowerCase())
+    expect(SUT).toBe('Given pattern is found at index 0')
+  })
+  it('expects to return a message when there is no pattern', () => {
+    const text = 'ABCDEFG'
+    const pattern = 'AEG'
+    const SUT = checkIfPatternExists(text.toLowerCase(), pattern.toLowerCase())
+    expect(SUT).toBe(undefined)
+  })
+  it('expects to find a pattern independent of casing', () => {
+    const text = 'AbCAAAAAAB'
+    const pattern = 'abc'
+    const SUT = checkIfPatternExists(text, pattern)
+    expect(SUT).toBe(undefined)
+  })
+  it('expects to throw an error message when given inpuut is not a string', () => {
+    const text = 123444456
+    const pattern = 123
+    expect(() => checkIfPatternExists(text, pattern)).toThrow('Given input is not a string')
+  })
+})