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Add an example for IgnoreFields (#205)
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Add an example for IgnoreFields. This resuses the test data from the example
in the cmp package to provide consistency between examples.
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colinnewell authored Oct 4, 2020
1 parent d713870 commit 566225a
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130 changes: 130 additions & 0 deletions cmp/cmpopts/example_test.go
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// Copyright 2020, The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package cmpopts_test

import (
"fmt"
"net"
"time"

"github.com/google/go-cmp/cmp"
"github.com/google/go-cmp/cmp/cmpopts"
"github.com/google/go-cmp/cmp/internal/flags"
)

func init() {
flags.Deterministic = true
}

// Use IgnoreFields to ignore fields on a struct type when comparing
// by providing a value of the type and the field names to ignore.
// Typically, a zero value of the type is used (e.g., foo.MyStruct{}).
func ExampleIgnoreFields_testing() {
// Let got be the hypothetical value obtained from some logic under test
// and want be the expected golden data.
got, want := MakeGatewayInfo()

// While the specified fields will be semantically ignored for the comparison,
// the fields may be printed in the diff when displaying entire values
// that are already determined to be different.
if diff := cmp.Diff(want, got, cmpopts.IgnoreFields(Client{}, "IPAddress")); diff != "" {
t.Errorf("MakeGatewayInfo() mismatch (-want +got):\n%s", diff)
}

// Output:
// MakeGatewayInfo() mismatch (-want +got):
// cmpopts_test.Gateway{
// SSID: "CoffeeShopWiFi",
// - IPAddress: s"192.168.0.2",
// + IPAddress: s"192.168.0.1",
// NetMask: {0xff, 0xff, 0x00, 0x00},
// Clients: []cmpopts_test.Client{
// ... // 3 identical elements
// {Hostname: "espresso", ...},
// {Hostname: "latte", LastSeen: s"2009-11-10 23:00:23 +0000 UTC", ...},
// + {
// + Hostname: "americano",
// + IPAddress: s"192.168.0.188",
// + LastSeen: s"2009-11-10 23:03:05 +0000 UTC",
// + },
// },
// }
}

type (
Gateway struct {
SSID string
IPAddress net.IP
NetMask net.IPMask
Clients []Client
}
Client struct {
Hostname string
IPAddress net.IP
LastSeen time.Time
}
)

func MakeGatewayInfo() (x, y Gateway) {
x = Gateway{
SSID: "CoffeeShopWiFi",
IPAddress: net.IPv4(192, 168, 0, 1),
NetMask: net.IPv4Mask(255, 255, 0, 0),
Clients: []Client{{
Hostname: "ristretto",
IPAddress: net.IPv4(192, 168, 0, 116),
}, {
Hostname: "aribica",
IPAddress: net.IPv4(192, 168, 0, 104),
LastSeen: time.Date(2009, time.November, 10, 23, 6, 32, 0, time.UTC),
}, {
Hostname: "macchiato",
IPAddress: net.IPv4(192, 168, 0, 153),
LastSeen: time.Date(2009, time.November, 10, 23, 39, 43, 0, time.UTC),
}, {
Hostname: "espresso",
IPAddress: net.IPv4(192, 168, 0, 121),
}, {
Hostname: "latte",
IPAddress: net.IPv4(192, 168, 0, 219),
LastSeen: time.Date(2009, time.November, 10, 23, 0, 23, 0, time.UTC),
}, {
Hostname: "americano",
IPAddress: net.IPv4(192, 168, 0, 188),
LastSeen: time.Date(2009, time.November, 10, 23, 3, 5, 0, time.UTC),
}},
}
y = Gateway{
SSID: "CoffeeShopWiFi",
IPAddress: net.IPv4(192, 168, 0, 2),
NetMask: net.IPv4Mask(255, 255, 0, 0),
Clients: []Client{{
Hostname: "ristretto",
IPAddress: net.IPv4(192, 168, 0, 116),
}, {
Hostname: "aribica",
IPAddress: net.IPv4(192, 168, 0, 104),
LastSeen: time.Date(2009, time.November, 10, 23, 6, 32, 0, time.UTC),
}, {
Hostname: "macchiato",
IPAddress: net.IPv4(192, 168, 0, 153),
LastSeen: time.Date(2009, time.November, 10, 23, 39, 43, 0, time.UTC),
}, {
Hostname: "espresso",
IPAddress: net.IPv4(192, 168, 0, 121),
}, {
Hostname: "latte",
IPAddress: net.IPv4(192, 168, 0, 221),
LastSeen: time.Date(2009, time.November, 10, 23, 0, 23, 0, time.UTC),
}},
}
return x, y
}

var t fakeT

type fakeT struct{}

func (t fakeT) Errorf(format string, args ...interface{}) { fmt.Printf(format+"\n", args...) }

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