test(otel): Add unit test for otel package

otel/go.mod

@@ -5,6 +5,7 @@ go 1.23.4
 require (
 	github.com/Scalingo/go-utils/errors/v2 v2.4.0
 	github.com/kelseyhightower/envconfig v1.4.0
+	github.com/stretchr/testify v1.10.0
 	go.opentelemetry.io/otel v1.34.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.34.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp v1.34.0
@@ -15,11 +16,13 @@ require (
 
 require (
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.25.1 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/otel/metric v1.34.0 // indirect
 	go.opentelemetry.io/otel/trace v1.34.0 // indirect
@@ -32,4 +35,5 @@ require (
 	google.golang.org/grpc v1.69.4 // indirect
 	google.golang.org/protobuf v1.36.3 // indirect
 	gopkg.in/errgo.v1 v1.0.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

otel/go.sum

@@ -71,6 +71,9 @@ google.golang.org/grpc v1.69.4 h1:MF5TftSMkd8GLw/m0KM6V8CMOCY6NZ1NQDPGFgbTt4A=
 google.golang.org/grpc v1.69.4/go.mod h1:vyjdE6jLBI76dgpDojsFGNaHlxdjXN9ghpnd2o7JGZ4=
 google.golang.org/protobuf v1.36.3 h1:82DV7MYdb8anAVi3qge1wSnMDrnKK7ebr+I0hHRN1BU=
 google.golang.org/protobuf v1.36.3/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/errgo.v1 v1.0.1 h1:oQFRXzZ7CkBGdm1XZm/EbQYaYNNEElNBOd09M6cqNso=
 gopkg.in/errgo.v1 v1.0.1/go.mod h1:3NjfXwocQRYAPTq4/fzX+CwUhPRcR/azYRhj8G+LqMo=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

otel/otel_test.go

@@ -0,0 +1,77 @@
+package otel
+
+import (
+	"context"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNew(t *testing.T) {
+	tests := []struct {
+		name        string
+		reinit      bool
+		env         map[string]string
+		expectError string
+	}{
+		{
+			name:        "initialization without service_name defined should result in error",
+			expectError: "required key OTEL_SERVICE_NAME missing value",
+		},
+		{
+			name: "minimal initialization",
+			env: map[string]string{
+				"OTEL_SERVICE_NAME": "test",
+			},
+		},
+		{
+			name:   "re-initialization to check singleton usage",
+			reinit: true,
+			env: map[string]string{
+				"OTEL_SERVICE_NAME": "test",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Cleanup(func() {
+				globalProviders = nil
+				globalOnce = sync.Once{}
+			})
+
+			ctx := context.Background()
+
+			if test.env != nil {
+				for k, v := range test.env {
+					t.Setenv(k, v)
+				}
+			}
+
+			err := New(ctx)
+			if test.expectError != "" {
+				require.Error(t, err)
+				assert.Contains(t, err.Error(), test.expectError)
+
+				require.Nil(t, globalProviders)
+			} else {
+				require.NoError(t, err)
+
+				require.NotNil(t, globalProviders)
+				assert.NotNil(t, globalProviders.meterProvider)
+
+				// Check when reinitializing the SDK
+				if test.reinit {
+					previousGlobalProviders := *globalProviders
+
+					err = New(ctx)
+					require.NoError(t, err)
+					// Check that pointer are the same
+					assert.Equal(t, previousGlobalProviders, *globalProviders)
+				}
+			}
+		})
+	}
+}