collector/netdev_linux_test.go: Add compatibility tests

To prepare for the introduction of new metric names, add tests for the legacy
metric names and values. This will make it easier to ensure that the code that
converts the new metrics to the old ones (for compatibility) behaves correctly.

Signed-off-by: Benoît Knecht <bknecht@protonmail.ch>

collector/netdev_linux_test.go

@@ -127,6 +127,37 @@ var links = []rtnetlink.LinkMessage{
 			},
 		},
 	},
+	{
+		Attributes: &rtnetlink.LinkAttributes{
+			Name: "enp0s0f0",
+			Stats64: &rtnetlink.LinkStats64{
+				RXPackets:         226,
+				TXPackets:         803,
+				RXBytes:           231424,
+				TXBytes:           822272,
+				RXErrors:          14,
+				TXErrors:          2,
+				RXDropped:         10,
+				TXDropped:         17,
+				Multicast:         285,
+				Collisions:        30,
+				RXLengthErrors:    5,
+				RXOverErrors:      3,
+				RXCRCErrors:       1,
+				RXFrameErrors:     4,
+				RXFIFOErrors:      6,
+				RXMissedErrors:    21,
+				TXAbortedErrors:   22,
+				TXCarrierErrors:   7,
+				TXFIFOErrors:      24,
+				TXHeartbeatErrors: 9,
+				TXWindowErrors:    19,
+				RXCompressed:      23,
+				TXCompressed:      20,
+				RXNoHandler:       62,
+			},
+		},
+	},
 }
 
 func TestNetDevStatsIgnore(t *testing.T) {
@@ -146,7 +177,7 @@ func TestNetDevStatsIgnore(t *testing.T) {
 		t.Errorf("want netstat tun0 packets %v, got %v", want, got)
 	}
 
-	if want, got := 9, len(netStats); want != got {
+	if want, got := 10, len(netStats); want != got {
 		t.Errorf("want count of devices to be %d, got %d", want, got)
 	}
 
@@ -174,3 +205,74 @@ func TestNetDevStatsAccept(t *testing.T) {
 		t.Error("want fixture interface 💩0 to exist, but it does not")
 	}
 }
+
+func TestNetDevLegacyMetricNames(t *testing.T) {
+	expected := []string{
+		"receive_packets",
+		"transmit_packets",
+		"receive_bytes",
+		"transmit_bytes",
+		"receive_errs",
+		"transmit_errs",
+		"receive_drop",
+		"transmit_drop",
+		"receive_multicast",
+		"transmit_colls",
+		"receive_frame",
+		"receive_fifo",
+		"transmit_carrier",
+		"transmit_fifo",
+		"receive_compressed",
+		"transmit_compressed",
+	}
+
+	filter := newDeviceFilter("", "")
+	netStats := netlinkStats(links, &filter, log.NewNopLogger())
+
+	for dev, devStats := range netStats {
+		for _, name := range expected {
+			if _, ok := devStats[name]; !ok {
+				t.Errorf("metric %s should be defined on interface %s", name, dev)
+			}
+		}
+	}
+}
+
+func TestNetDevLegacyMetricValues(t *testing.T) {
+	expected := map[string]uint64{
+		"receive_packets":     226,
+		"transmit_packets":    803,
+		"receive_bytes":       231424,
+		"transmit_bytes":      822272,
+		"receive_errs":        14,
+		"transmit_errs":       2,
+		"receive_drop":        10 + 21,
+		"transmit_drop":       17,
+		"receive_multicast":   285,
+		"transmit_colls":      30,
+		"receive_frame":       5 + 3 + 1 + 4,
+		"receive_fifo":        6,
+		"transmit_carrier":    22 + 7 + 9 + 19,
+		"transmit_fifo":       24,
+		"receive_compressed":  23,
+		"transmit_compressed": 20,
+	}
+
+	filter := newDeviceFilter("", "^enp0s0f0$")
+	netStats := netlinkStats(links, &filter, log.NewNopLogger())
+	metrics, ok := netStats["enp0s0f0"]
+	if !ok {
+		t.Error("expected stats for interface enp0s0f0")
+	}
+
+	for name, want := range expected {
+		got, ok := metrics[name]
+		if !ok {
+			t.Errorf("metric %s should be defined on interface enp0s0f0", name)
+			continue
+		}
+		if want != got {
+			t.Errorf("want %s %d, got %d", name, want, got)
+		}
+	}
+}