github.com/shopspring/decimal: different values produced by FromString and FromFloat

I'm trying to use gomock to mock an interface that takes a decimal. The usecase:

v, err := decimal.NewFromString(order.Value)
if err != nil {
	return err
}

if err := p.CDI.CreateBuyEvent(ctx, v); err != nil {
	return err
}

And in the tests:

value := decimal.NewFromFloat64(1000)
cfg.cdi.EXPECT().CreateBuyEvent(ctx, value).Return(nil)

Running this, I get:

expected call doesn't match the argument at index 1.
   Got: 1000 (entities.Order)
   Want: is equal to 1000 (entities.Order)

However, if I instead instantiate the decimal using NewFromString("1000") in the tests, it passes. My question is: why is the underlying value different for NewFromString and NewFromFloat?

Because the two values happen to have different memory representations while logically containing the same values.

Use the Equal method to compare shopspring.Decimal values.

Demonstration:

package main

import (
	"fmt"

	"github.com/shopspring/decimal"
)

func main() {
	fs, err := decimal.NewFromString("1000")
	if err != nil {
		panic(err)
	}

	ff := decimal.NewFromFloat(1000)
	if ff != fs {
		fmt.Printf("%#v != %#v\n", fs, ff)
	}

	fmt.Println(ff.Equal(fs))
}

Produces:

decimal.Decimal{value:(*big.Int)(0xc0001103a0), exp:0} != decimal.Decimal{value:(*big.Int)(0xc0001103c0), exp:3}
true

Playground.

I would add that there's no need to rush for SO to ask a question like this: you should have first performed at least minimal debugging.
Really, if you have two values which must be the same but they do not compare equal using the == operator which is dumb — it compares struct vaues field-wise, — just see what the values actually contain.