Rewrite ERS test using new infrastructure

Also, minor fix to ERS test: use explicit integer division (//) so that it will
work with python3

Test suite: None
Test baseline: N/A
Test namelist changes: N/A
Test status: N/A

Fixes: None

User interface changes?: No

Code review: None

utils/python/CIME/SystemTests/ers.py

@@ -1,67 +1,67 @@
 """
-CIME restart test  This class inherits from SystemTestsCommon
+CIME restart test
 """
 from CIME.XML.standard_module_setup import *
-from CIME.SystemTests.system_tests_common import SystemTestsCommon
+from CIME.SystemTests.system_tests_compare_two import SystemTestsCompareTwo
 
 logger = logging.getLogger(__name__)
 
-class ERS(SystemTestsCommon):
+class ERS(SystemTestsCompareTwo):
 
     def __init__(self, case):
         """
         initialize an object interface to the ERS system test
         """
-        SystemTestsCommon.__init__(self, case)
+        SystemTestsCompareTwo.__init__(self, case,
+                                       two_builds_for_sharedlib = False,
+                                       two_builds_for_model = False,
+                                       run_one_suffix = 'base',
+                                       run_two_suffix = 'rest',
+                                       run_one_description = 'initial run',
+                                       run_two_description = 'restart test')
 
-    def _ers_first_phase(self):
-        stop_n      = self._case.get_value("STOP_N")
-        stop_option = self._case.get_value("STOP_OPTION")
-        expect(stop_n > 0, "Bad STOP_N: %d" % stop_n)
+        self._stop_option = self._case.get_value("STOP_OPTION")
+        self._stop_n = self._case.get_value("STOP_N")
 
-        # Move to config_tests.xml once that's ready
-        rest_n = stop_n/2 + 1
-        self._case.set_value("REST_N", rest_n)
-        self._case.set_value("REST_OPTION", stop_option)
-        self._case.set_value("HIST_N", stop_n)
-        self._case.set_value("HIST_OPTION", stop_option)
-        self._case.set_value("CONTINUE_RUN", False)
-        self._case.flush()
+        # Need stop_n > 2 in order to have at least one time unit both before
+        # and after restart
+        expect(self._stop_n > 2, "ERROR: stop_n value %d too short"%self._stop_n)
+
+        self._rest_n = self._get_rest_n()
+
+    def _get_rest_n(self):
+        """
+        Return an int giving rest_n for this test.
+
+        Assumes that self._stop_n is already set.
+        """
+
+        rest_n = self._stop_n // 2 + 1
+        expect(rest_n > 0, "ERROR: stop_n value %d generates rest_n too short: %d"
+               %(self._stop_n, rest_n))
+        return rest_n
 
-        expect(stop_n > 2, "ERROR: stop_n value %d too short"%stop_n)
+    def _run_common_setup(self):
+        self._case.set_value("HIST_OPTION", self._stop_option)
+        self._case.set_value("HIST_N", self._stop_n)
+
+    def _run_one_setup(self):
+        # We shouldn't need to set STOP_N here, but we make this explicit for
+        # symmetry with _run_two_setup
+        self._case.set_value("STOP_N", self._stop_n)
+        self._case.set_value("CONTINUE_RUN", False)
+        self._case.set_value("REST_OPTION", self._stop_option)
+        self._case.set_value("REST_N", self._rest_n)
         logger.info("doing an %s %s initial test with restart file at %s %s"
                     %(str(stop_n), stop_option, str(rest_n), stop_option))
-        return SystemTestsCommon.run(self)
 
-    def _ers_second_phase(self):
-        stop_n      = self._case.get_value("STOP_N")
-        stop_option = self._case.get_value("STOP_OPTION")
-
-        rest_n = stop_n/2 + 1
-        stop_new = stop_n - rest_n
-        expect(stop_new > 0, "ERROR: stop_n value %d too short %d %d"%(stop_new,stop_n,rest_n))
+    def _run_two_setup(self):
+        stop_new = self._stop_n - self._rest_n
+        expect(stop_new > 0, "ERROR: stop_n value %d too short %d %d"
+               %(stop_new, self._stop_n, self._rest_n))
 
         self._case.set_value("STOP_N", stop_new)
         self._case.set_value("CONTINUE_RUN", True)
         self._case.set_value("REST_OPTION","never")
-        self._case.flush()
         logger.info("doing an %s %s restart test"
                     %(str(stop_n), stop_option))
-        success = SystemTestsCommon._run(self, "rest")
-
-        # Compare restart file
-        if success:
-            return self._component_compare_test("base", "rest")
-        else:
-            return False
-
-    def run(self):
-        success = self._ers_first_phase()
-
-        if success:
-            return self._ers_second_phase()
-        else:
-            return False
-
-    def report(self):
-        SystemTestsCommon.report(self)