Simple test of Perflib unmarshalling

collector/perflib.go

@@ -63,10 +63,14 @@ func unmarshalObject(obj *perflib.PerfObject, vs interface{}) error {
 
 			ctr, found := counters[tag]
 			if !found {
-				log.Debugf("missing counter %q, has %v", tag, counters)
+				log.Debugf("missing counter %q, have %v", tag, counterMapKeys(counters))
+				continue
 			}
 			if !target.Field(i).CanSet() {
-				return fmt.Errorf("tagged field %v cannot be written to", f)
+				return fmt.Errorf("tagged field %v cannot be written to", f.Name)
+			}
+			if fieldType := target.Field(i).Type(); fieldType != reflect.TypeOf((*float64)(nil)).Elem() {
+				return fmt.Errorf("tagged field %v has wrong type %v, must be float64", f.Name, fieldType)
 			}
 
 			switch ctr.Def.CounterType {
@@ -86,3 +90,11 @@ func unmarshalObject(obj *perflib.PerfObject, vs interface{}) error {
 
 	return nil
 }
+
+func counterMapKeys(m map[string]*perflib.PerfCounter) []string {
+	keys := make([]string, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	return keys
+}

collector/perflib_test.go

@@ -0,0 +1,125 @@
+package collector
+
+import (
+	"reflect"
+	"testing"
+
+	perflibCollector "github.com/leoluk/perflib_exporter/collector"
+	"github.com/leoluk/perflib_exporter/perflib"
+)
+
+type simple struct {
+	ValA float64 `perflib:"Something"`
+	ValB float64 `perflib:"Something Else"`
+}
+
+func TestUnmarshalPerflib(t *testing.T) {
+	cases := []struct {
+		name string
+		obj  *perflib.PerfObject
+
+		expectedOutput []simple
+		expectError    bool
+	}{
+		{
+			name:           "nil check",
+			obj:            nil,
+			expectedOutput: []simple{},
+			expectError:    true,
+		},
+		{
+			name: "Simple",
+			obj: &perflib.PerfObject{
+				Instances: []*perflib.PerfInstance{
+					{
+						Counters: []*perflib.PerfCounter{
+							{
+								Def: &perflib.PerfCounterDef{
+									Name:        "Something",
+									CounterType: perflibCollector.PERF_COUNTER_COUNTER,
+								},
+								Value: 123,
+							},
+						},
+					},
+				},
+			},
+			expectedOutput: []simple{{ValA: 123}},
+			expectError:    false,
+		},
+		{
+			name: "Multiple properties",
+			obj: &perflib.PerfObject{
+				Instances: []*perflib.PerfInstance{
+					{
+						Counters: []*perflib.PerfCounter{
+							{
+								Def: &perflib.PerfCounterDef{
+									Name:        "Something",
+									CounterType: perflibCollector.PERF_COUNTER_COUNTER,
+								},
+								Value: 123,
+							},
+							{
+								Def: &perflib.PerfCounterDef{
+									Name:        "Something Else",
+									CounterType: perflibCollector.PERF_COUNTER_COUNTER,
+								},
+								Value: 256,
+							},
+						},
+					},
+				},
+			},
+			expectedOutput: []simple{{ValA: 123, ValB: 256}},
+			expectError:    false,
+		},
+		{
+			name: "Multiple instances",
+			obj: &perflib.PerfObject{
+				Instances: []*perflib.PerfInstance{
+					{
+						Counters: []*perflib.PerfCounter{
+							{
+								Def: &perflib.PerfCounterDef{
+									Name:        "Something",
+									CounterType: perflibCollector.PERF_COUNTER_COUNTER,
+								},
+								Value: 321,
+							},
+						},
+					},
+					{
+						Counters: []*perflib.PerfCounter{
+							{
+								Def: &perflib.PerfCounterDef{
+									Name:        "Something",
+									CounterType: perflibCollector.PERF_COUNTER_COUNTER,
+								},
+								Value: 231,
+							},
+						},
+					},
+				},
+			},
+			expectedOutput: []simple{{ValA: 321}, {ValA: 231}},
+			expectError:    false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			output := make([]simple, 0)
+			err := unmarshalObject(c.obj, &output)
+			if err != nil && !c.expectError {
+				t.Errorf("Did not expect error, got %q", err)
+			}
+			if err == nil && c.expectError {
+				t.Errorf("Expected an error, but got ok")
+			}
+
+			if err == nil && !reflect.DeepEqual(output, c.expectedOutput) {
+				t.Errorf("Output mismatch, expected %+v, got %+v", c.expectedOutput, output)
+			}
+		})
+	}
+}