How to create and use my own golang package locally to get this test to run?

I'm new to golang working through coding exercises and I have all the following files in a directory called leap. I'm using gvm to run the golang executable (version 1.4), using a command such as "go test leap_test.go".

When I do go test leap_test.go I get the following results:

# command-line-arguments
leap_test.go:5:2: open /home/user/go/leap/leap: no such file or directory
FAIL	command-line-arguments [setup failed]

1. How do I include the IsLeap() function so that the tests run correctly.
2. Why is cases_test.go even included? It seems like leap_test.go is all you'd need for tests.

cases_test.go

package leap

// Source: exercism/x-common
// Commit: 945d08e Merge pull request #50 from soniakeys/master

var testCases = []struct {
	year        int
	expected    bool
	description string
}{
	{1996, true, "leap year"},
	{1997, false, "non-leap year"},
	{1998, false, "non-leap even year"},
	{1900, false, "century"},
	{2400, true, "fourth century"},
	{2000, true, "Y2K"},
}

leap_test.go

package leap

import (
	"testing"
	"./leap"
)

var testCases = []struct {
	year        int
	expected    bool
	description string
}{
	{1996, true, "a vanilla leap year"},
	{1997, false, "a normal year"},
	{1900, false, "a century"},
	{2400, true, "an exceptional century"},
}

    func TestLeapYears(t *testing.T) {
    	for _, test := range testCases {
    		observed := IsLeap(test.year)
    		if observed != test.expected {
    			t.Fatalf("%v is %s", test.year, test.description)
    		}
    	}
    }

leap.go

package leap

import(
	"fmt"
)

func IsLeap(year int) bool {
  return true
}

> Command go
>
> Test packages
>
> Usage:
>
> go test [-c] [-i] [build and test flags] [packages] [flags for test binary]

For example,

leap/leap.go

package leap

func IsLeap(year int) bool {
	return true
}

leap/leap_test.go

package leap

import (
	"testing"
)

var testCases = []struct {
	year        int
	expected    bool
	description string
}{
	{1996, true, "a vanilla leap year"},
	{1997, false, "a normal year"},
	{1900, false, "a century"},
	{2400, true, "an exceptional century"},
}

func TestLeapYears(t *testing.T) {
	for _, test := range testCases {
		observed := IsLeap(test.year)
		if observed != test.expected {
			t.Fatalf("%v is %s", test.year, test.description)
		}
	}
}

If $GOPATH is set to include the leap package directory:

$ go test leap
--- FAIL: TestLeapYears (0.00s)
	leap_test.go:22: 1997 is a normal year
FAIL
FAIL	leap	0.003s
$

Or, if you cd to the leap package directory:

$ go test
--- FAIL: TestLeapYears (0.00s)
	leap_test.go:22: 1997 is a normal year
FAIL
exit status 1
FAIL	so/leap	0.003s
$