From 5e0bfcc2b0f6059cd7bbf3ad7230208c4615c8bf Mon Sep 17 00:00:00 2001
From: Bryan Van Deusen <bryan.vandeusen@fabledsword.com>
Date: Tue, 14 Apr 2026 22:27:08 -0400
Subject: [PATCH] test(host_agent): pure-function tests for metric expansion

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../host_agent/test_routes_expand_metrics.py  | 98 +++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 tests/plugins/host_agent/test_routes_expand_metrics.py

diff --git a/tests/plugins/host_agent/test_routes_expand_metrics.py b/tests/plugins/host_agent/test_routes_expand_metrics.py
new file mode 100644
index 0000000..92bd300
--- /dev/null
+++ b/tests/plugins/host_agent/test_routes_expand_metrics.py
@@ -0,0 +1,98 @@
+"""Pure-function tests for host_agent metric expansion."""
+from datetime import datetime, timezone
+
+from plugins.host_agent.routes import _expand_sample_to_metrics
+
+
+NOW = datetime(2026, 4, 14, 12, 0, 0, tzinfo=timezone.utc)
+
+
+def _sample() -> dict:
+    return {
+        "ts": NOW.isoformat(),
+        "cpu_pct": 12.5,
+        "mem": {
+            "total_bytes": 16_000_000_000,
+            "used_bytes":       8_000_000_000,
+            "available_bytes":  8_000_000_000,
+            "swap_used_bytes": 0,
+        },
+        "load": {"1m": 0.1, "5m": 0.2, "15m": 0.3},
+        "uptime_secs": 1234,
+        "storage": [
+            {"mount": "/",         "total_bytes": 1000, "used_bytes": 400},
+            {"mount": "/mnt/data", "total_bytes": 2000, "used_bytes": 1800},
+        ],
+    }
+
+
+def _by_metric(rows, name):
+    return [r for r in rows if r.metric_name == name]
+
+
+def test_expand_emits_cpu_mem_load_uptime():
+    rows = _expand_sample_to_metrics(_sample(), "testhost", NOW)
+    names = {r.metric_name for r in rows}
+    assert "cpu_pct" in names
+    assert "mem_used_pct" in names
+    assert "mem_available_bytes" in names
+    assert "swap_used_bytes" in names
+    assert "load_1m" in names and "load_5m" in names and "load_15m" in names
+    assert "uptime_secs" in names
+
+
+def test_expand_source_module_and_recorded_at():
+    rows = _expand_sample_to_metrics(_sample(), "testhost", NOW)
+    assert rows, "expected non-empty rows"
+    for r in rows:
+        assert r.source_module == "host_agent"
+        assert r.recorded_at == NOW
+
+
+def test_expand_cpu_value_and_resource():
+    cpu = _by_metric(_expand_sample_to_metrics(_sample(), "testhost", NOW), "cpu_pct")
+    assert len(cpu) == 1
+    assert cpu[0].value == 12.5
+    assert cpu[0].resource_name == "testhost"
+
+
+def test_expand_mem_used_pct_math():
+    # used = total - available = 50%
+    used = _by_metric(_expand_sample_to_metrics(_sample(), "testhost", NOW), "mem_used_pct")
+    assert len(used) == 1
+    assert abs(used[0].value - 50.0) < 0.01
+
+
+def test_expand_per_mount_disk_metrics():
+    rows = _expand_sample_to_metrics(_sample(), "testhost", NOW)
+    per_mount = _by_metric(rows, "disk_used_pct")
+    assert {r.resource_name for r in per_mount} == {"testhost:/", "testhost:/mnt/data"}
+    # Values: / is 40%, /mnt/data is 90%
+    by_res = {r.resource_name: r.value for r in per_mount}
+    assert abs(by_res["testhost:/"] - 40.0) < 0.01
+    assert abs(by_res["testhost:/mnt/data"] - 90.0) < 0.01
+
+
+def test_expand_disk_worst_is_max():
+    worst = _by_metric(_expand_sample_to_metrics(_sample(), "testhost", NOW), "disk_used_pct_worst")
+    assert len(worst) == 1
+    assert worst[0].resource_name == "testhost"
+    assert abs(worst[0].value - 90.0) < 0.01
+
+
+def test_expand_skips_missing_cpu_and_load():
+    sample = {"mem": {"total_bytes": 100, "available_bytes": 50}}
+    rows = _expand_sample_to_metrics(sample, "h", NOW)
+    names = {r.metric_name for r in rows}
+    assert "cpu_pct" not in names
+    assert "load_1m" not in names
+    assert "uptime_secs" not in names
+    assert "mem_used_pct" in names
+
+
+def test_expand_empty_storage_emits_no_disk_worst():
+    sample = {"cpu_pct": 1.0, "storage": []}
+    rows = _expand_sample_to_metrics(sample, "h", NOW)
+    names = {r.metric_name for r in rows}
+    assert "disk_used_pct_worst" not in names
+    assert "cpu_pct" in names