Add test for file source and target

spec/connection_spec.lua

@@ -0,0 +1,26 @@
+local vips = require "vips"
+local ffi = require "ffi"
+
+local JPEG_FILE = "./spec/images/Gugg_coloured.jpg"
+-- test gvalue
+describe("test connection", function()
+    local tmpdir, svg, jpeg, webp, tempfile
+
+    setup(function()
+        -- vips.log.enable(true)
+    end)
+
+    describe("to file target", function()
+        it("can create image from file source and write to file target", function()
+            local source = vips.Source.new_from_file(JPEG_FILE)
+            local image = vips.Image.new_from_source(source, '', { access = 'sequential' })
+            local filename = ffi.os == "Windows" and os.getenv("TMP") .. "\\x.png" or "/tmp/x.png"
+            local target = vips.Target.new_to_file(filename)
+            image:write_to_target(target, '.png')
+
+            local image1 = vips.Image.new_from_file(JPEG_FILE, { access = 'sequential' })
+            local image2 = vips.Image.new_from_file(filename, { access = 'sequential' })
+            assert.is_true((image1 - image2):abs():max() < 10)
+        end)
+    end)
+end)