[test] Add a clr_rapl test matching current code

This patch adds a test for the nrm/coolr/clr_rapl.py code, based on
the __main__ code added to it recently. This is an example of how the
modules should be tested automatically, instead of relying on __main__
snippets everywhere.

We should replace those snippets bits by bits by tests similar to this
one. The end goal is to able to active a gitlab pipeline that validate
merge requests automatically.

test/test_clr_rapl.py

+"""Tests for the Coolr RAPL module."""
+import nrm
+import nrm.coolr
+import nrm.coolr.clr_rapl
+import pytest
+
+
+@pytest.fixture
+def rapl_reader():
+    """Fixture for a regular rapl reader."""
+    rr = nrm.coolr.clr_rapl.rapl_reader()
+    assert rr.initialized(), "no rapl sysfs detected"
+    return rr
+
+
+def test_read_powerdomains(rapl_reader):
+    """Ensure we can read the power domains."""
+    assert rapl_reader.get_powerdomains()
+
+
+def test_get_powerlimits(rapl_reader):
+    """Ensure we can read the power limits."""
+    data = rapl_reader.get_powerlimits()
+    for k in data:
+        if data[k]['enabled']:
+            break
+    else:
+        assert False, "No power domain enabled."
+
+
+def test_set_powerlimits(rapl_reader):
+    """Ensure we can set a power limit."""
+    data = rapl_reader.get_powerlimits()
+    for k in data:
+        if data[k]['enabled']:
+            # compute a new limit in between cur and max
+            newlim = (data[k]['maxW'] - data[k]['curW'])/2.0
+    rapl_reader.set_powerlimit_pkg(newlim)
+
+
+def test_sample(rapl_reader):
+    """Ensure we can sample power consumption properly."""
+    import time
+    rapl_reader.start_energy_counter()
+    for i in range(0, 3):
+        time.sleep(1)
+        assert rapl_reader.sample(accflag=True)
+    rapl_reader.stop_energy_counter()
+    assert rapl_reader.total_energy_json()