FAQ
FYI
I am on Hadoop 0.20.2, JUnit 4


Varene Olivier a écrit :
Hello to all,

first of all many thanks for this great piece of software you are all
contributing to :)

I am actually creating a program in Hadoop MapReduce, but I intend to
massively use JUnit Tests to validate my code.

To test a Mapper, I mock a Mapper.Context object and run the Mapper.map
function with it, but inside my Mapper.map function, I am using Counters
to maintain internal statistics. The update of those counters make the
test fails with a null pointer (JavaNullPointerException).
There is an issue "Counters" of variable visibility from my test ...

Do you have any idea how to mock/validate/overcome this issue ?



Thanks a lots
Best Regards
Olivier Varene


: Code :
--------

private static enum Counters {NBLINES};
private static IntWritable one = new IntWritable(1);
private static LongWritable oneL = new LongWritable(1);


// Mapper
/**
* outputs 1 for each line encountered
*/
public static class LCMapper extends
Mapper<LongWritable, Text, IntWritable, LongWritable>
{
private final static IntWritable one = new IntWritable(1);
private final static LongWritable oneL = new LongWritable(1);
/**
* for each line encountered outputs 1 for the key 1
*/
public void map(LongWritable p_key, Text p_inputs, Context p_context)
throws IOException, InterruptedException
{
p_context.getCounter(Counters.NBLINES).increment(1);
p_context.write(one,oneL);
} // end map
} // end Mapper

: Test :
--------

@Test
public void testLCMapper() throws IOException, InterruptedException
{
LCMapper mapper = new LCMapper();
Text value = new Text("ligneA\nlignB\n");
// mock the map job execution context
Context context = mock(Context.class);
try {
mapper.map(null, value, context);
} catch (NullPointerException e)
{
// exception raised by context.getCounter(...) null pointer
// HOW TO MOCK ???
// Counter is a static enum from the englobing class ...
// issue with variable visibility (from map function) in this test
}
// verify that the Mapper issued (one,oneL) pair
verify(context).write(one,oneL);

} // end testLCMapper

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postedMay 27, '10 at 8:34a
activeMay 28, '10 at 12:48p
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