Test FUSE and HgBackingStore stat collection

Summary:
I am refactoring edenfs' EdenStats class. In doing so, I accidentally removed a call to `aggregate`, causing `flushStatsNow` to not expose accurate counters. This wasn't caught by any existing tests, only by manual testing.

Add some tests to prevent FUSE and HgBackingStore statistics collection from completely regressing.

Reviewed By: simpkins

Differential Revision: D15274275

fbshipit-source-id: c8a9c9848dd60aee7f252a93f10ddce6d7560799

eden/integration/stats_test.py

@@ -14,6 +14,63 @@ from .lib import testcase
 from .lib.hgrepo import HgRepository
 
 
+class FUSEStatsTest(testcase.EdenRepoTest):
+    def test_reading_committed_file_bumps_read_counter(self) -> None:
+        counters_before = self.get_counters()
+        path = Path(self.mount) / "file"
+        path.read_bytes()
+        counters_after = self.get_counters()
+
+        self.assertGreater(
+            counters_after.get("fuse.read_us.count", 0),
+            counters_before.get("fuse.read_us.count", 0),
+            f"Reading {path} should increment fuse.read_us.count",
+        )
+
+    def test_writing_untracked_file_bumps_write_counter(self) -> None:
+        counters_before = self.get_counters()
+        path = Path(self.mount) / "new_file"
+        path.write_bytes(b"hello")
+        counters_after = self.get_counters()
+
+        self.assertGreater(
+            counters_after.get("fuse.write_us.count", 0),
+            counters_before.get("fuse.write_us.count", 0),
+            f"Writing to {path} should increment fuse.write_us.count",
+        )
+
+    def create_repo(self, name: str) -> HgRepository:
+        return self.create_hg_repo(name)
+
+    def populate_repo(self) -> None:
+        self.repo.write_file("file", "hello world!\n")
+        self.repo.commit("Initial commit.")
+
+
+class HgBackingStoreStatsTest(testcase.EdenRepoTest):
+    def test_reading_file_gets_file_from_hg(self) -> None:
+        counters_before = self.get_counters()
+        path = Path(self.mount) / "dir" / "subdir" / "file"
+        path.read_bytes()
+        counters_after = self.get_counters()
+
+        self.assertEqual(
+            counters_after.get("store.hg.get_file.count", 0),
+            counters_before.get("store.hg.get_file.count", 0) + 1,
+            f"Reading {path} should increment store.hg.get_file.count",
+        )
+
+    def create_repo(self, name: str) -> HgRepository:
+        return self.create_hg_repo(name)
+
+    def populate_repo(self) -> None:
+        # This file evades EdenFS' automatic prefetching by being two levels
+        # inside the root.
+        self.repo.write_file("dir/subdir/file", "hello world!\n")
+
+        self.repo.commit("Initial commit.")
+
+
 class HgImporterStatsTest(testcase.EdenRepoTest):
     def test_reading_file_imports_blob(self) -> None:
         counters_before = self.get_counters()