Add tests for the initializer

init_test.go

@@ -0,0 +1,175 @@
+package gotoprom
+
+import (
+	"testing"
+
+	"github.com/cabify/gotoprom/prometheusvanilla"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestInitializer_MustAddBuilder(t *testing.T) {
+	t.Run("adds builder", func(t *testing.T) {
+		initializer := NewInitializer(prometheus.NewRegistry())
+		initializer.MustAddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+
+		err := initializer.Init(&struct {
+			Metric func() prometheus.Gauge `name:"gauge" help:"help"`
+		}{}, "namespace")
+		assert.NoError(t, err)
+	})
+	t.Run("same builder twice panics", func(t *testing.T) {
+		initializer := NewInitializer(prometheus.NewRegistry())
+		initializer.MustAddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+
+		assert.Panics(t, func() {
+			initializer.MustAddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+		})
+	})
+}
+
+func TestInitializer_AddBuilder(t *testing.T) {
+	t.Run("same builder twice fails", func(t *testing.T) {
+		initializer := NewInitializer(prometheus.NewRegistry())
+		err := initializer.AddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+		assert.NoError(t, err)
+
+		err = initializer.AddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+		assert.Error(t, err)
+	})
+}
+
+func TestInitializer_MustInit(t *testing.T) {
+	t.Run("happy case", func(t *testing.T) {
+		initializer := NewInitializer(prometheus.NewRegistry())
+
+		structPtr := &struct{}{}
+		assert.NotPanics(t, func() {
+			initializer.MustInit(structPtr, "namespace")
+		})
+	})
+
+	t.Run("panics when can't init", func(t *testing.T) {
+		initializer := NewInitializer(prometheus.NewRegistry())
+
+		notAPointer := struct{}{}
+		assert.Panics(t, func() {
+			initializer.MustInit(notAPointer, "namespace")
+		})
+	})
+}
+
+func TestInitializer_Init(t *testing.T) {
+	someInt := 3
+	type someLabels struct {
+		Label string `label:"label"`
+	}
+	type someLabelsWithoutLabelTag struct {
+		LabelWithoutLabelTag string
+	}
+	t.Run("fails", func(t *testing.T) {
+		for _, tc := range []struct {
+			desc    string
+			metrics interface{}
+		}{
+			{
+				desc:    "not a pointer to struct",
+				metrics: struct{}{},
+			},
+			{
+				desc:    "pointer to a non struct",
+				metrics: &someInt,
+			},
+			{
+				desc: "contains a non-supported field, like a string",
+				metrics: &struct {
+					Something string
+				}{},
+			},
+			{
+				desc: "sub-struct doesn't define its namespace",
+				metrics: &struct {
+					Inner struct{}
+				}{},
+			},
+			{
+				desc: "sub-struct can't be initialized",
+				metrics: &struct {
+					Inner struct {
+						Deeper struct{} `thisdoesnothaveanamespace:"nothing"`
+					} `namespace:"thishasanamespace"`
+				}{},
+			},
+			{
+				desc: "non-exported field",
+				metrics: &struct {
+					foo func() prometheus.Gauge `name:"unexported" help:"this can't be set"`
+				}{},
+			},
+			{
+				desc: "missing name",
+				metrics: &struct {
+					Foo func() prometheus.Gauge `help:"missing name tag"`
+				}{},
+			},
+			{
+				desc: "missing help",
+				metrics: &struct {
+					Foo func() prometheus.Gauge `name:"nohelp"`
+				}{},
+			},
+			{
+				desc: "more than one return argument",
+				metrics: &struct {
+					Foo func() (prometheus.Gauge, error) `name:"toomanyreturnargs" help:"what is this?"`
+				}{},
+			},
+			{
+				desc: "no builders defined",
+				metrics: &struct {
+					Foo func() prometheus.Counter `name:"unknowntype" help:"Counter is not registered"`
+				}{},
+			},
+			{
+				desc: "builder fails",
+				metrics: &struct {
+					Foo func() prometheus.Summary `name:"unknowntype" help:"max_age is malformed" max_age:"bar"`
+				}{},
+			},
+			{
+				desc: "builder fails",
+				metrics: &struct {
+					Foo func() prometheus.Summary `name:"unknowntype" help:"max_age is malformed" max_age:"bar"`
+				}{},
+			},
+			{
+				desc: "too many params",
+				metrics: &struct {
+					Foo func(someLabels, string) prometheus.Gauge `name:"too many input params" help:"only labels are accepted"`
+				}{},
+			},
+			{
+				desc: "labels without label tag",
+				metrics: &struct {
+					Foo func(someLabelsWithoutLabelTag) prometheus.Gauge `name:"nolabeltag" help:"This labels are missing the label tag"`
+				}{},
+			},
+			{
+				desc: "metric registration fails",
+				metrics: &struct {
+					Foo func() prometheus.Gauge `name:"metric" help:"first gauge"`
+					Bar func() prometheus.Gauge `name:"metric" help:"name duplicates the previous one"`
+				}{},
+			},
+		} {
+			t.Run(tc.desc, func(t *testing.T) {
+				initializer := NewInitializer(prometheus.NewRegistry())
+				initializer.MustAddBuilder(prometheusvanilla.GaugeType, prometheusvanilla.BuildGauge)
+				initializer.MustAddBuilder(prometheusvanilla.SummaryType, prometheusvanilla.BuildSummary)
+
+				err := initializer.Init(tc.metrics, "namespace")
+				assert.Error(t, err)
+			})
+		}
+	})
+}