write integration tests

[milianw]

we need to write some tests that check the integration of the perfparser utility library

[milianw]

We need to do something along the following lines:

• write a utility header that launches perf on a given debuggee. this should already have launch perf from hotspot #11 in mind so that we can reuse the same code in the future
• write some integration tests using the existing test-clients (cpp-inlining, cpp-recursion)

the integration tests would basically boil down to:

• run perf record on a test client in a given configuration i.e.:
  • without call graphs
  • with --call-graph dwarf
  • with --event cycles
  • with --event cycles,instructions (probably for the future, I'm working on that in support multiple perf event sources #14)
• parse the resulting perf.data file
• verify that we get some meaningful data back, i.e.:
  • summary shouldn't be empty, potentially even compare to system values if they are easy to get. but since this can be run on many machines, don't hardcode the checks
  • do some sanity checks on the sample counts, but don't check on explicit numbers since these will fluctuate
  • do some sanity checks on the resulting top-down / bottom-up graphs. i.e. ensure that the hotspots are found and that their call graphs look same
  • also check the contents of the caller/callee results

for the model checks at the end, we may reuse parts of the code that I've written for the existing model tests