Add basic tests

plugins/processors/snmp_lookup/lookup.go

@@ -68,7 +68,7 @@ func (l *Lookup) Init() (err error) {
 	}
 
 	switch l.Translator {
-	case "gosmi":
+	case "", "gosmi":
 		if l.translator, err = si.NewGosmiTranslator(l.Path, l.Log); err != nil {
 			return fmt.Errorf("loading translator: %w", err)
 		}

plugins/processors/snmp_lookup/lookup_test.go

@@ -0,0 +1,99 @@
+package snmp_lookup
+
+import (
+	"testing"
+
+	"github.com/influxdata/telegraf/internal/snmp"
+	"github.com/influxdata/telegraf/plugins/common/parallel"
+	si "github.com/influxdata/telegraf/plugins/inputs/snmp"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInit(t *testing.T) {
+	tests := []struct {
+		name     string
+		plugin   Lookup
+		expected string
+	}{
+		{
+			name: "defaults",
+			plugin: Lookup{
+				AgentTag:        "source",
+				IndexTag:        "index",
+				CacheSize:       defaultCacheSize,
+				ParallelLookups: defaultParallelLookups,
+				ClientConfig:    *snmp.DefaultClientConfig(),
+				CacheTTL:        defaultCacheTTL,
+			},
+		},
+		{
+			name: "empty",
+		},
+		{
+			name: "wrong SNMP client config",
+			plugin: Lookup{
+				ClientConfig: snmp.ClientConfig{
+					Version: 99,
+				},
+			},
+			expected: "parsing SNMP client config: invalid version",
+		},
+		{
+			name: "netsnmp translator",
+			plugin: Lookup{
+				ClientConfig: snmp.ClientConfig{
+					Translator: "netsnmp",
+				},
+			},
+		},
+		{
+			name: "unknown translator",
+			plugin: Lookup{
+				ClientConfig: snmp.ClientConfig{
+					Translator: "unknown",
+				},
+			},
+			expected: `invalid agent.snmp_translator value "unknown"`,
+		},
+		{
+			name: "table init",
+			plugin: Lookup{
+				Tags: []si.Field{
+					{
+						Name: "ifName",
+						Oid:  ".1.3.6.1.2.1.31.1.1.1.1",
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.plugin.Log = testutil.Logger{}
+
+			if tt.expected == "" {
+				require.NoError(t, tt.plugin.Init())
+			} else {
+				require.ErrorContains(t, tt.plugin.Init(), tt.expected)
+			}
+		})
+	}
+}
+
+func TestStart(t *testing.T) {
+	acc := &testutil.NopAccumulator{}
+	p := Lookup{}
+	require.NoError(t, p.Init())
+
+	p.Ordered = true
+	require.NoError(t, p.Start(acc))
+	require.IsType(t, &parallel.Ordered{}, p.parallel)
+	p.Stop()
+
+	p.Ordered = false
+	require.NoError(t, p.Start(acc))
+	require.IsType(t, &parallel.Unordered{}, p.parallel)
+	p.Stop()
+}