Refactor and add tests (fixes #2963) (#2964)

src/test/java/com/thealgorithms/maths/FFTTest.java

@@ -0,0 +1,147 @@
+package com.thealgorithms.maths;
+import org.junit.jupiter.api.Test;
+import java.util.ArrayList;
+import static org.junit.jupiter.api.Assertions.*;
+
+class FFTTest {
+
+    // Testing the simple function getReal
+    @Test
+    void getRealtest()
+    {
+        FFT.Complex complex = new FFT.Complex(1.0,1.0);
+        assertEquals(1.0,complex.getReal());
+    }
+
+    // Testing the simple function getImaginary
+    @Test
+    void getImaginaryTest()
+    {
+        FFT.Complex complex = new FFT.Complex();
+        assertEquals(0.0,complex.getImaginary());
+    }
+
+    // Testing the function add, assertEqual test
+    @Test
+    void addTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(1.0,1.0);
+        FFT.Complex complex2 = new FFT.Complex(2.0,2.0);
+        double add = complex1.add(complex2).getReal();
+        assertEquals(3.0,add);
+    }
+
+    // Testing the function add, assertNotEqual test
+    @Test
+    void addFalseTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(1.0,1.0);
+        FFT.Complex complex2 = new FFT.Complex(2.0,2.0);
+        double add = complex1.add(complex2).getReal();
+        assertNotEquals(2.0,add);
+    }
+
+    // Testing the function substract, assertEqual test
+    @Test
+    void subtractTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        FFT.Complex complex2 = new FFT.Complex(1.0,1.0);
+        double sub = complex1.subtract(complex2).getReal();
+        assertEquals(1.0,sub);
+    }
+
+    // Testing the function multiply complex, assertEqual test
+    @Test
+    void multiplyWithComplexTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        FFT.Complex complex2 = new FFT.Complex(1.0,1.0);
+        double multiReal = complex1.multiply(complex2).getReal();
+        double multiImg = complex1.multiply(complex2).getImaginary();
+        assertEquals(0.0,multiReal);
+        assertEquals(4.0,multiImg);
+    }
+
+    // Testing the function multiply scalar, assertEqual test
+    @Test
+    void multiplyWithScalarTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+
+        double multiReal = complex1.multiply(2).getReal();
+        double multiImg = complex1.multiply(3).getImaginary();
+        assertEquals(4.0,multiReal);
+        assertEquals(6.0,multiImg);
+    }
+
+    // Testing the function conjugate, assertEqual test
+    @Test
+    void conjugateTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        double conReal = complex1.conjugate().getReal();
+        double conImg = complex1.conjugate().getImaginary();
+        assertEquals(2.0,conReal);
+        assertEquals(-2.0,conImg);
+    }
+
+    // Testing the function abs, assertEqual test
+    @Test
+    void abs()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,3.0);
+        double abs = complex1.abs();
+        assertEquals(Math.sqrt(13),abs);
+    }
+
+    // Testing the function divide complex, assertEqual test.
+    @Test
+    void divideWithComplexTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        FFT.Complex complex2 = new FFT.Complex(1.0,2.0);
+        double divReal = complex1.divide(complex2).getReal();
+        double divImg = complex1.divide(complex2).getImaginary();
+        assertEquals(1.2,divReal);
+        assertEquals(-0.4,divImg);
+    }
+
+    // Testing the function divide scalar, assertEqual test.
+    @Test
+    void divideWithScalarTest()
+    {
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        double divReal = complex1.divide(2).getReal();
+        double divImg = complex1.divide(2).getImaginary();
+        assertEquals(1,divReal);
+        assertEquals(1,divImg);
+    }
+
+    // Testing the function fft, assertEqual test.
+    // https://scistatcalc.blogspot.com/2013/12/fft-calculator.html used this link to
+    // ensure the result
+    @Test
+    void fft()
+    {
+        ArrayList<FFT.Complex> arr = new ArrayList<FFT.Complex>();
+        FFT.Complex complex1 = new FFT.Complex(2.0,2.0);
+        FFT.Complex complex2 = new FFT.Complex(1.0,3.0);
+        FFT.Complex complex3 = new FFT.Complex(3.0,1.0);
+        FFT.Complex complex4 = new FFT.Complex(2.0,2.0);
+
+        arr.add(complex1);
+        arr.add(complex2);
+        arr.add(complex3);
+        arr.add(complex4);
+        arr = FFT.fft(arr,false);
+        double realV1= arr.get(0).getReal();
+        double realV2= arr.get(2).getReal();
+        double imgV1 = arr.get(0).getImaginary();
+        double imgV2 = arr.get(2).getImaginary();
+        assertEquals(8.0,realV1);
+        assertEquals(2.0,realV2);
+        assertEquals(8.0, imgV1);
+        assertEquals(-2.0,imgV2);
+    }
+}