Package org.djunits.util

Class ArrayMathTest

java.lang.Object

org.djunits.util.ArrayMathTest

public class ArrayMathTest
extends Object

Unit tests for ArrayMath. The suite aims for 100% line and branch coverage by exercising:

• All functional (allocating) operations: add, add(a,c), subtract, scaleBy, abs, axpy, multiply, divide, reciprocal
• All procedural (into-buffer) operations: addInto, scaleInto, axpyInto
• All error paths: NullPointerException for null inputs and IllegalArgumentException for length mismatches
• Edge behavior: empty arrays, in-place destinations (out == a and/or out == b), division by zero and NaN, reciprocal of 0 and Infinity
• Coverage of the private constructor via reflection

Design: Each test documents the scenario and the expected outcome. An assertArrayClose helper is used with a tight tolerance for floating-point comparisons. Copyright (c) 2025-2026 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://djunits.org. The DJUNITS project is distributed under a three-clause BSD-style license.

Author:

Alexander Verbraeck (specifications); Test implementation by Copilot.

Constructor Summary

Constructors

Constructor	Description
ArrayMathTest()

Method Summary

Modifier and Type	Method	Description
(package private) void	absFunctional()	Verifies ArrayMath.abs(double[]) absolute value, including negative zero and NaN.
(package private) void	addArraysFunctional()	Verifies ArrayMath.add(double[], double[]) on a happy path and length/Null preconditions.
(package private) void	addIntoProcedural()	Verifies ArrayMath.addInto(double[], double[], double[]).
(package private) void	addScalarFunctional()	Verifies ArrayMath.add(double[], double) adds a constant to each element and returns a new array.
(package private) void	axpyFunctional()	Verifies fused AXPY ArrayMath.axpy(double[], double[], double) and preconditions.
(package private) void	axpyIntoProcedural()	Verifies ArrayMath.axpyInto(double[], double[], double, double[]).
(package private) void	constructorIsNotInstantiableButReachableViaReflection()	Covers the private no-arg constructor of ArrayMath to achieve 100% coverage of the class.
(package private) void	divideFunctional()	Verifies ArrayMath.divide(double[], double[]) element-wise division, including division by zero and NaN.
(package private) void	multiplyFunctional()	Verifies ArrayMath.multiply(double[], double[]) element-wise product and preconditions.
(package private) void	reciprocalFunctional()	Verifies ArrayMath.reciprocal(double[]) including reciprocal of 0 and Infinity.
(package private) void	scaleByFunctional()	Verifies ArrayMath.scaleBy(double[], double) scaling by a scalar and preconditions.
(package private) void	scaleIntoProcedural()	Verifies ArrayMath.scaleInto(double[], double, double[]).
(package private) void	subtractFunctional()	Verifies ArrayMath.subtract(double[], double[]) element-wise difference and preconditions.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ArrayMathTest

public ArrayMathTest()

Method Details

constructorIsNotInstantiableButReachableViaReflection

@Test
void constructorIsNotInstantiableButReachableViaReflection()
                                                    throws Exception

Covers the private no-arg constructor of ArrayMath to achieve 100% coverage of the class.

Throws:

Exception - when reflection fails (should not happen in normal environments)

addArraysFunctional

@Test
void addArraysFunctional()

Verifies ArrayMath.add(double[], double[]) on a happy path and length/Null preconditions. Expected: element-wise sum, new array returned; NPE/IAE on invalid inputs.

addScalarFunctional

@Test
void addScalarFunctional()

Verifies ArrayMath.add(double[], double) adds a constant to each element and returns a new array. Also checks empty array path and null precondition.

subtractFunctional

@Test
void subtractFunctional()

Verifies ArrayMath.subtract(double[], double[]) element-wise difference and preconditions.

scaleByFunctional

@Test
void scaleByFunctional()

Verifies ArrayMath.scaleBy(double[], double) scaling by a scalar and preconditions.

absFunctional

@Test
void absFunctional()

Verifies ArrayMath.abs(double[]) absolute value, including negative zero and NaN.

axpyFunctional

@Test
void axpyFunctional()

Verifies fused AXPY ArrayMath.axpy(double[], double[], double) and preconditions.

multiplyFunctional

@Test
void multiplyFunctional()

Verifies ArrayMath.multiply(double[], double[]) element-wise product and preconditions.

divideFunctional

@Test
void divideFunctional()

Verifies ArrayMath.divide(double[], double[]) element-wise division, including division by zero and NaN.

reciprocalFunctional

@Test
void reciprocalFunctional()

Verifies ArrayMath.reciprocal(double[]) including reciprocal of 0 and Infinity.

addIntoProcedural

@Test
void addIntoProcedural()

Verifies ArrayMath.addInto(double[], double[], double[]).

• Normal usage with distinct output buffer
• In-place usage with out == a
• In-place usage with out == b
• All precondition error paths

scaleIntoProcedural

@Test
void scaleIntoProcedural()

Verifies ArrayMath.scaleInto(double[], double, double[]).

• Normal usage with distinct output buffer
• In-place usage with out == a
• Null and length precondition errors

axpyIntoProcedural

@Test
void axpyIntoProcedural()

Verifies ArrayMath.axpyInto(double[], double[], double, double[]).

• Normal usage with distinct output buffer
• In-place usage with out == a
• In-place usage with out == b
• All precondition error paths