Add tests for env provider

env.go

@@ -54,13 +54,16 @@ func (ep *EnvProvider) Name() string {
 
 // Fill takes struct fields and fills their values
 func (ep *EnvProvider) Fill(in *Input) error {
-	content, err := ep.envMap()
+	envs, err := ep.envMap()
 	if err != nil {
 		return err
 	}
+	if len(envs) == 0 {
+		return nil
+	}
 
 	for _, f := range in.Fields {
-		value, err := ep.provide(content, f.Tags.Config, f.Path)
+		value, err := ep.provide(envs, f.Tags.Config, f.Path)
 		if err != nil {
 			if errors.Is(err, ErrKeyNotFound) {
 				continue
@@ -84,15 +87,15 @@ func (ep *EnvProvider) Fill(in *Input) error {
 func (ep *EnvProvider) envMap() (map[string]string, error) {
 	envs := envFromOS()
 	var fileEnvs map[string]string
-	var err error
 
 	if ep.Source != "" {
+		var err error
 		fileEnvs, err = envFromFile(ep.Source)
-	}
-	if err != nil {
-		notExistsErr := errors.Is(err, os.ErrNotExist)
-		if (notExistsErr && ep.Required) || !notExistsErr {
-			return nil, err
+		if err != nil {
+			notExistsErr := errors.Is(err, os.ErrNotExist)
+			if (notExistsErr && ep.Required) || !notExistsErr {
+				return nil, err
+			}
 		}
 	}
 

env_test.go

@@ -0,0 +1,188 @@
+package gonfig
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewEnvProvider(t *testing.T) {
+	ep := NewEnvProvider()
+	require.NotNil(t, ep)
+	assert.Equal(t, "", ep.EnvPrefix)
+	assert.Equal(t, true, ep.SnakeCase)
+	assert.Equal(t, true, ep.UpperCase)
+	assert.Equal(t, "_", ep.FieldSeparator)
+	assert.Equal(t, "", ep.Source)
+	assert.Equal(t, false, ep.Required)
+}
+
+func TestEnvProvider_Name(t *testing.T) {
+	ep := NewEnvProvider()
+	assert.Equal(t, "ENV provider", ep.Name())
+}
+
+func TestEnvProvider_Fill(t *testing.T) {
+	t.Run("env file existence", func(t *testing.T) {
+		s := struct{}{}
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := EnvProvider{
+			Source:   "NotExistingFile",
+			Required: false,
+		}
+
+		err = ep.Fill(in)
+		assert.NoError(t, err)
+
+		ep.Required = true
+		err = ep.Fill(in)
+		assert.Error(t, err)
+	})
+
+	t.Run("prioritize OS envs", func(t *testing.T) {
+		os.Clearenv()
+		err := os.Setenv("OS", "env from os")
+		require.NoError(t, err)
+
+		s := struct {
+			Priority string
+			Os       string
+			File     string
+		}{}
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := NewEnvProvider()
+		ep.Source = "testdata/.env"
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "FILE", s.Priority)
+		assert.Equal(t, "env from os", s.Os)
+		assert.Equal(t, "env from file", s.File)
+
+		err = os.Setenv("PRIORITY", "OS")
+		require.NoError(t, err)
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "OS", s.Priority)
+	})
+
+	t.Run("should be set", func(t *testing.T) {
+		os.Clearenv()
+
+		s := struct {
+			Env1 string
+			Env2 int
+			Env3 bool
+		}{}
+		for i, v := range []string{"env1", "2", "false"} {
+			err := os.Setenv("ENV"+fmt.Sprint(i+1), v)
+			require.NoError(t, err)
+		}
+
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := NewEnvProvider()
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+
+		for _, f := range in.Fields {
+			assert.True(t, f.IsSet)
+		}
+	})
+
+	t.Run("env prefix", func(t *testing.T) {
+		os.Clearenv()
+		err := os.Setenv("APP_Env", "env")
+		require.NoError(t, err)
+
+		s := struct {
+			Env string
+		}{}
+
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := EnvProvider{
+			EnvPrefix: "APP_",
+		}
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "env", s.Env)
+	})
+
+	t.Run("snake case", func(t *testing.T) {
+		os.Clearenv()
+		err := os.Setenv("Env_Var", "env")
+		require.NoError(t, err)
+
+		s := struct {
+			EnvVar string
+		}{}
+
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := EnvProvider{
+			SnakeCase: true,
+		}
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "env", s.EnvVar)
+	})
+
+	t.Run("upper case", func(t *testing.T) {
+		os.Clearenv()
+		err := os.Setenv("ENV", "env")
+		require.NoError(t, err)
+
+		s := struct {
+			Env string
+		}{}
+
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := EnvProvider{
+			UpperCase: true,
+		}
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "env", s.Env)
+	})
+
+	t.Run("field separator", func(t *testing.T) {
+		os.Clearenv()
+		err := os.Setenv("NestedEnvVar", "env")
+		require.NoError(t, err)
+
+		s := struct {
+			Nested struct {
+				EnvVar string
+			}
+		}{}
+
+		in, err := NewInput(&s)
+		require.NoError(t, err)
+		require.NotNil(t, in)
+		ep := EnvProvider{
+			FieldSeparator: "",
+		}
+
+		err = ep.Fill(in)
+		require.NoError(t, err)
+		assert.Equal(t, "env", s.Nested.EnvVar)
+	})
+}

testdata/.env

@@ -0,0 +1,2 @@
+PRIORITY=FILE
+FILE="env from file"