describe("splitfilename", function()
	local nextfile = require "nextfile"

	it("should return the filename and extension of an absolute filepath", function()
		local dir, name, ext = nextfile.splitfilename("/testdir/701.txt")

		assert.are.equal("/testdir/", dir)
		assert.are.equal("701", name)
		assert.are.equal(".txt", ext)
	end)

	it("should return the filename and extension of a relative filepath", function()
		local dir, name, ext = nextfile.splitfilename("../../foo/testdir/file.mp3")

		assert.are.equal("../../foo/testdir/", dir)
		assert.are.equal("file", name)
		assert.are.equal(".mp3", ext)
	end)
end)

describe("nextletter", function()
	local nextfile = require "nextfile"

	it("should return the next letter when the current letter is not 'z'", function()
		local letter = nextfile.nextletter("q")

		assert.are.equal("r", letter)
	end)

	it("should return 'za' when the current letter is 'z'", function()
		local letter = nextfile.nextletter("z")

		assert.are.equal("za", letter)
	end)
end)

describe("nextfile", function()
	local prevfile = require "prevfile"
	local nextfile = require "nextfile"

	insulate("prevfile.prevfile returns nil", function()
		prevfile.prevfile = function() return nil end

		it("should call prevfile.prevfile", function()
			spy.on(prevfile, "prevfile")
			test_directory = "/testdir"

			nextfile.nextfile(test_directory)

			assert.spy(prevfile.prevfile).was_called_with(test_directory)
		end)

		it("should return nil", function()
			local file = nextfile.nextfile("/testdir")

			assert.are.equal(nil, file)
		end)
	end)

	insulate("prevfile.prevfile returns a numeric filename", function()
		prevfile.prevfile = function() return "/testdir/701.txt" end

		it("should return the result of incrementing the filename", function()
			local file = nextfile.nextfile("/testdir")

			assert.are.equal("/testdir/702.txt", file)
		end)
	end)

	insulate("prevfile.prevfile returns a non-numeric filename", function()
		it("should return the result of replacing the last character with the next letter of the alphabet", function()
			prevfile.prevfile = function() return "/testdir/421b.txt" end

			local file = nextfile.nextfile("/testdir")

			assert.are.equal("/testdir/421c.txt", file)
		end)

		it("should return the result of replacing z with za when z is the last letter of the filename", function()
			prevfile.prevfile = function() return "/testdir/421z.txt" end

			local file = nextfile.nextfile("/testdir")

			assert.are.equal("/testdir/421za.txt", file)
		end)
	end)
end)