Refactor FibonacciJavaStreams and add unit tests (#4260)

DIRECTORY.md

@@ -608,6 +608,7 @@
             * [EggDroppingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EggDroppingTest.java)
             * [KnapsackMemoizationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackMemoizationTest.java)
             * [LevenshteinDistanceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LevenshteinDistanceTests.java)
+            * [MinimumPathSumTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/MinimumPathSumTest.java)
             * [OptimalJobSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/OptimalJobSchedulingTest.java)
             * [PartitionProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/PartitionProblemTest.java)
             * [SubsetCountTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/SubsetCountTest.java)
@@ -637,6 +638,7 @@
             * [FactorialTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FactorialTest.java)
             * [FastInverseSqrtTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FastInverseSqrtTests.java)
             * [FFTTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FFTTest.java)
+            * [FibonacciJavaStreamsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciJavaStreamsTest.java)
             * [FibonacciNumberCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciNumberCheckTest.java)
             * [FindMaxTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindMaxTest.java)
             * [FindMinTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FindMinTest.java)
@@ -673,6 +675,7 @@
             * [SquareRootWithNewtonRaphsonTestMethod](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SquareRootWithNewtonRaphsonTestMethod.java)
             * [StandardDeviationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/StandardDeviationTest.java)
             * [StandardScoreTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/StandardScoreTest.java)
+            * [SumOfArithmeticSeriesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumOfArithmeticSeriesTest.java)
             * [SumOfDigitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumOfDigitsTest.java)
             * [SumWithoutArithmeticOperatorsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumWithoutArithmeticOperatorsTest.java)
             * [TestArmstrong](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/TestArmstrong.java)

src/main/java/com/thealgorithms/maths/FibonacciJavaStreams.java

@@ -2,7 +2,6 @@ package com.thealgorithms.maths;
 
 import java.math.BigDecimal;
 import java.util.List;
-import java.util.Objects;
 import java.util.Optional;
 import java.util.stream.Stream;
 
@@ -14,7 +13,7 @@ public class FibonacciJavaStreams {
 
     public static Optional<BigDecimal> calculate(final BigDecimal index) {
         if (index == null || index.compareTo(BigDecimal.ZERO) < 0) {
-            return Optional.empty();
+            throw new IllegalArgumentException("Input index cannot be null or negative!");
         }
 
         if (index.compareTo(BigDecimal.ONE) < 0) {
@@ -30,72 +29,4 @@ public class FibonacciJavaStreams {
 
         return results.isEmpty() ? Optional.empty() : Optional.of(results.get(results.size() - 1));
     }
-
-    public static void assertThat(final Object actual, final Object expected) {
-        if (!Objects.equals(actual, expected)) {
-            throw new AssertionError(String.format("expected=%s but was actual=%s", expected, actual));
-        }
-    }
-
-    public static void main(final String[] args) {
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(-1));
-            assertThat(result.isEmpty(), true);
-        }
-        {
-            final Optional<BigDecimal> result = calculate(BigDecimal.ZERO);
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, BigDecimal.ZERO));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(BigDecimal.ONE);
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(2));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(3));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(2)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(10));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(55)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(20));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(6765)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(30));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(832040)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(40));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(102334155)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(50));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal(12586269025L)));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(100));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal("354224848179261915075")));
-        }
-        {
-            final Optional<BigDecimal> result = calculate(new BigDecimal(200));
-            assertThat(result.isPresent(), true);
-            result.ifPresent(value -> assertThat(value, new BigDecimal("280571172992510140037611932413038677189525")));
-        }
-    }
 }

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

@@ -0,0 +1,71 @@
+package com.thealgorithms.maths;
+
+import java.math.BigDecimal;
+import java.util.Optional;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author Albina Gimaletdinova on 25/07/2023
+ */
+public class FibonacciJavaStreamsTest {
+    private static final String EXCEPTION_MESSAGE = "Input index cannot be null or negative!";
+
+    @Test
+    public void testWithNegativeIndexShouldThrowException() {
+        Exception exception = Assertions.assertThrows(IllegalArgumentException.class, () -> FibonacciJavaStreams.calculate(new BigDecimal(-1)));
+        Assertions.assertEquals(EXCEPTION_MESSAGE, exception.getMessage());
+    }
+
+    @Test
+    public void testCheckTheFirst4SequenceElements() {
+        checkElement(BigDecimal.ZERO, BigDecimal.ZERO);
+        checkElement(BigDecimal.ONE, BigDecimal.ONE);
+        checkElement(new BigDecimal(2), BigDecimal.ONE);
+        checkElement(new BigDecimal(3), new BigDecimal(2));
+    }
+
+    @Test
+    public void testCheck10thSequenceElement() {
+        checkElement(new BigDecimal(10), new BigDecimal(55));
+    }
+
+    @Test
+    public void testCheck20thSequenceElement() {
+        checkElement(new BigDecimal(20), new BigDecimal(6765));
+    }
+
+    @Test
+    public void testCheck30thSequenceElement() {
+        checkElement(new BigDecimal(30), new BigDecimal(832040));
+    }
+
+    @Test
+    public void testCheck40thSequenceElement() {
+        checkElement(new BigDecimal(40), new BigDecimal(102334155));
+    }
+
+    @Test
+    public void testCheck50thSequenceElement() {
+        checkElement(new BigDecimal(50), new BigDecimal(12586269025L));
+    }
+
+    @Test
+    public void testCheck100thSequenceElement() {
+        checkElement(new BigDecimal(100), new BigDecimal("354224848179261915075"));
+    }
+
+    @Test
+    public void testCheck200thSequenceElement() {
+        checkElement(new BigDecimal(200), new BigDecimal("280571172992510140037611932413038677189525"));
+    }
+
+    private static void checkElement(BigDecimal index, BigDecimal expected) {
+        // when
+        Optional<BigDecimal> result = FibonacciJavaStreams.calculate(index);
+
+        // then
+        Assertions.assertTrue(result.isPresent());
+        Assertions.assertEquals(result.get(), expected);
+    }
+}