You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: populate_test.go
    path of file: ./repos/fx
    
    the code of the file until where you have to start completion: // Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package fx_test

import (
	"io"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	. "go.uber.org/fx"
	"go.uber.org/fx/fxtest"
)

func TestPopulate(t *testing.T) {
	t.Parallel()

	// We make sure t1 has a size so when we compare pointers, 2 different
	// objects are not equal.
	type t1 struct {
		buf [1024]byte
	}
	type t2 struct{}

	_ = new(t1).buf // buf is unused

	t.Run("populate nothing", func(t *testing.T) {
		t.Parallel()

		app := fxtest.New(t,
			Provide(func() *t1 { panic("should not be called ") }),
			Populate(),
		)
		app.RequireStart().RequireStop()
	})

	t.Run("populate single", func(t *testing.T) {
		t.Parallel()

		var v1 *t1
		app := fxtest.New(t,
			Provide(func() *t1 { return &t1{} }),
			Populate(&v1),
		)
		app.RequireStart().RequireStop()
		require.NotNil(t, v1, "did not populate value")
	})

	t.Run("populate interface", func(t *testing.T) {
		t.Parallel()

		var reader io.Reader
		app := fxtest.New(t,
			Provide(func() io.Reader { return strings.NewReader("hello world") }),
			Populate(&reader),
		)
		app.RequireStart().RequireStop()

		bs, err := io.Read
    
func TestPopulate(t *testing.T) {
	t.Parallel()

	// We make sure t1 has a size so when we compare pointers, 2 different
	// objects are not equal.
	type t1 struct {
		buf [1024]byte
	}
	type t2 struct{}

	_ = new(t1).buf // buf is unused

	t.Run("populate nothing", func(t *testing.T) {
		t.Parallel()

		app := fxtest.New(t,
			Provide(func() *t1 { panic("should not be called ") }),
			Populate(),
		)
		app.RequireStart().RequireStop()
	})

	t.Run("populate single", func(t *testing.T) {
		t.Parallel()

		var v1 *t1
		app := fxtest.New(t,
			Provide(func() *t1 { return &t1{} }),
			Populate(&v1),
		)
		app.RequireStart().RequireStop()
		require.NotNil(t, v1, "did not populate value")
	})

	t.Run("populate interface", func(t *testing.T) {
		t.Parallel()

		var reader io.Reader
		app := fxtest.New(t,
			Provide(func() io.Reader { return strings.NewReader("hello world") }),
			Populate(&reader),
		)
		app.RequireStart().RequireStop()

		bs, err := io.ReadAll(reader)
		require.NoError(t, err, "Failed to use populated io.Reader")
		assert.Equal(t, "hello world", string(bs), "Unexpected reader")
	})

	t.Run("populate multiple inline values", func(t *testing.T) {
		t.Parallel()

		var (
			v1 *t1
			v2 *t2
		)
		app := fxtest.New(t,
			Provide(func() *t1 { return &t1{} }),
			Provide(func() *t2 { return &t2{} }),

			Populate(&v1),
			Populate(&v2),
		)
		app.RequireStart().RequireStop()

		require.NotNil(t, v1, "did not populate argument 1")
		require.NotNil(t, v2, "did not populate argument 2")
	})

	t.Run("populate fx.In struct", func(t *testing.T) {
		t.Parallel()

		targets := struct {
			In

			V1 *t1
			V2 *t2
		}{}

		app := fxtest.New(t,
			Provide(func() *t1 { return &t1{} }),
			Provide(func() *t2 { return &t2{} }),

			Populate(&targets),
		)
		app.RequireStart().RequireStop()

		require.NotNil(t, targets.V1, "did not populate field 1")
		require.NotNil(t, targets.V2, "did not populate field 2")
	})

	t.Run("populate named field", func(t *testing.T) {
		t.Parallel()

		type result struct {
			Out

			V1 *t1 `name:"n1"`
			V2 *t1 `name:"n2"`
		}

		targets := struct {
			In

			V1 *t1 `name:"n1"`
			V2 *t1 `name:"n2"`
		}{}

		app := fxtest.New(t,
			Provide(func() result {
				return result{
					V1: &t1{},
					V2: &t1{},
				}
			}),

			Populate(&targets),
		)
		app.RequireStart().RequireStop()

		require.NotNil(t, targets.V1, "did not populate field 1")
		require.NotNil(t, targets.V2, "did not populate field 2")
		// Cannot use assert.Equal here as we want to compare pointers.
		assert.False(t, targets.V1 == targets.V2, "fields should be different")
	})

	t.Run("annotated populate", func(t *testing.T) {
		t.Parallel()

		type result struct {
			Out

			V1 *t1 `name:"n1"`
			V2 *t1 `name:"n2"`
		}
		var v1, v2 *t1
		app := fxtest.New(t,
			Provide(func() result {
				return result{
					V1: &t1{},
					V2: &t1{},
				}
			}),
			Populate(
				Annotate(
					&v1,
					ParamTags(`name:"n1"`),
				),
				Annotate(
					&v2,
					ParamTags(`name:"n2"`),
				),
			),
		)
		app.RequireStart().RequireStop()

		require.NotNil(t, v1, "did not populate argument 1")
		require.NotNil(t, v2, "did not populate argument 2")
		// Cannot use assert.Equal here as we want to compare pointers.
		assert.False(t, v1 == v2, "values should be different")
	})

	t.Run("annotated populate with annotated provide", func(t *testing.T) {
		t.Parallel()
		var v1, v2 *t1
		app := fxtest.New(t,
			Provide(
				Annotate(
					func() (*t1, *t1) {
						return &t1{}, &t1{}
					},
					ResultTags(`name:"n1"`, `name:"n2"`),
				),
			),
			Populate(
				Annotate(
					&v1,
					ParamTags(`name:"n1"`),
				),
				Annotate(
					&v2,
					ParamTags(`name:"n2"`),
				),
			),
		)
		app.RequireStart().RequireStop()

		require.NotNil(t, v1, "did not populate argument 1")
		require.NotNil(t, v2, "did not populate argument 2")
		// Cannot use assert.Equal here as we want to compare pointers.
		assert.False(t, v1 == v2, "values should be different")
	})

	t.Run("populate group", func(t *testing.T) {
		t.Parallel()

		type result struct {
			Out

			V1 *t1 `group:"g"`
			V2 *t1 `group:"g"`
		}

		targets := struct {
			In

			Group []*t1 `group:"g"`
		}{}

		app := fxtest.New(t,
			Provide(func() result {
				return result{
					V1: &t1{},
					V2: &t1{},
				}
			}),

			Populate(&targets),
		)
		app.RequireStart().RequireStop()

		require.Len(t, targets.Group, 2, "Expected group to have 2 values")
		require.NotNil(t, targets.Group[0], "did not populate group value 1")
		require.NotNil(t, targets.Group[1], "did not populate group value 2")
		// Cannot use assert.Equal here as we want to compare pointers.
		assert.False(t, targets.Group[0] == targets.Group[1], "group values should be different")
	})
}