Question

this is my actual class I am writing test class below.

public class ReadFile {
private Scanner rx, tx;

public void openFile() {
    try {
        rx = new Scanner(new File("/sys/class/net/eth0/statistics/rx_bytes"));
        tx = new Scanner(new File("/sys/class/net/eth0/statistics/tx_bytes"));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public String readRxFile() {
    String rxData = "";
    while (rx.hasNext()) {
        rxData = rx.next();
    }

    return rxData;
}

public String readTxFile() {
    String txData = "";
    while (tx.hasNext()) {
        txData = tx.next();
    }
    return txData;
}

public void closeFile() {
    rx.close();
    tx.close();
}
}

this is test class. to test the read data.

public class Testreadrxfile extends TestCase {

public Testreadrxfile() {
    super();
}

protected void setUp() throws Exception {
    try {
        super.setUp();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

ReadFile rf;

public void testappdata() {
   String str1 = rf.readRxFile();
    Assert.assertEquals("14081",str1 );
}

}

this is the error I am getting.

java.lang.NullPointerException
atcom.android.deviceintelligence1.             test.Testreadrxfile.testappdata(Testreadrxfile.java:26)
at java.lang.reflect.Method.invokeNative(Native Method)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154)
at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:529)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1448)

this is not activity or service test to use getactivity() or getservice() so what I should do to get out of this error . thanks for help in advance.

Answer 1

see your code.. rf is not initialised..

ReadFile rf; // not intialisd

public void testappdata() {
   String str1 = rf.readRxFile(); // equivalent to null.readRxFile();
    Assert.assertEquals("14081",str1 );
}