TextFromStandardInputStream: Create tests that depends on input (System.in)

‘TextFromStandardInputStream’ class is used to create tests that depends on System input (System.in).

 

'provideLines' method is used to provide input to the program.

 

Arithmetic.java

package com.sample.app;

import java.util.Scanner;

public class Arithmetic {

	public int sum() {
		Scanner scanner = new Scanner(System.in);
		int a = scanner.nextInt();
		int b = scanner.nextInt();
		return a + b;
	}
}

As you see sum() method, it takes two integers a and b, return sum of a and b.

 

We can pass input 1, 2 using provideLines method like below.

@Rule
public final TextFromStandardInputStream systemInMock = emptyStandardInputStream();

systemInMock.provideLines("1", "2");

ArithmeticTest.java

package com.sample.app.tests;

import static org.junit.Assert.assertEquals;
import static org.junit.contrib.java.lang.system.TextFromStandardInputStream.emptyStandardInputStream;

import org.junit.Rule;
import org.junit.Test;
import org.junit.contrib.java.lang.system.TextFromStandardInputStream;

import com.sample.app.Arithmetic;

public class ArithmeticTest {
	@Rule
	public final TextFromStandardInputStream systemInMock = emptyStandardInputStream();

	private Arithmetic arithemtic = new Arithmetic();

	@Test
	public void sumOf1And2() {
		systemInMock.provideLines("1", "2");
		assertEquals(3, arithemtic.sum());
	}
}

You can download complete working application from this link.

https://github.com/harikrishna553/system-rules

 

 

  

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