NullPointerException when running JUnit tests, saying interface is null

NullPointerException when running JUnit tests, saying interface is null

I'm trying to write a java program that allows the user to input a series
of data values then for the program to sort through finding the mean and
the median of that series, using an interface to "treat" different objects
as if they were the same. However when I run my JUnit test, it keeps
saying my interface is null.
NoiseFilter.java
package noisefilter.model;
import java.util.ArrayList;
public interface NoiseFilter {
public double getBestMesurement(ArrayList<Double> samples);
}
AveragingFilter.java
package noisefilter.model;
import java.util.ArrayList;
public class AveragingFilter implements NoiseFilter {
@Override
/**
* The method getBestMeasurement takes an array list of type double and
returns a
*/
public double getBestMesurement(ArrayList<Double> samples) {
// TODO Auto-generated method stub
if (samples.equals(null)) {
throw new IllegalArgumentException("The Samples cannot be null");
}
if (samples.size() < 3) {
throw new IllegalArgumentException("The Sample size must have 3");
}
double sum = 0.0;
for (Double number : samples) {
sum += number;
}
return (sum / samples.size());
}
}
SensorData.java
package noisefilter.model;
import java.util.ArrayList;
public class SensorData implements NoiseFilter {
ArrayList<Double> data;
NoiseFilter filter;
public SensorData() {
this.data = new ArrayList<Double>();
this.filter = null;
}
public void addSample(double sample) {
data.add(sample);
}
public void setFilter(NoiseFilter filterVar) {
this.filter = filterVar;
}
public double getFilteredResult() {
if (filter.equals(null)) {
throw new IllegalStateException("The filter cannot be left null");
}
return filter.getBestMesurement(data);
}
@Override
public double getBestMesurement(ArrayList<Double> samples) {
samples = this.data;
return 0;
}
WhenAveragingFilter.java (JUnit Test)
package noisefilter.tests;
import static org.junit.Assert.*;
import org.junit.Before;
import org.junit.Test;
import noisefilter.model.NoiseFilter;
import noisefilter.model.SensorData;
public class WhenAverageFiltering {
NoiseFilter filter;
SensorData dataSet;
@Before
public void setUp() throws Exception {
this.dataSet = new SensorData();
dataSet.setFilter(filter);
}
@Test
public void averageOfThree100sShouldBe100() {
dataSet.addSample(100);
dataSet.addSample(100);
dataSet.addSample(100);
assertTrue(dataSet.getFilteredResult() == 100);
}
@Test
public void averageOfThreeDifferent() {
dataSet.addSample(120);
dataSet.addSample(140);
dataSet.addSample(130);
assertTrue(dataSet.getFilteredResult() == 130);
}
@Test
public void averageOfFiveDifferent() {
dataSet.addSample(10);
dataSet.addSample(50);
dataSet.addSample(60);
assertTrue(dataSet.getFilteredResult() == 40);
}
}
Here's the errors that I get when I run the JUnit Test.
java.lang.NullPointerException
at noisefilter.model.SensorData.getFilteredResult(SensorData.java:24)
at
noisefilter.tests.WhenAverageFiltering.averageOfFiveDifferent(WhenAverageFiltering.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at
org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at
org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at
org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)