Added unit tests for src/content/api.jl

Includes a @test_throws which verifies the bug in JuliaGizmos#109. This passes
before the fix:
Test Summary:  | Pass  Total
content! Tests |    7      7

test/api.jl

@@ -0,0 +1,35 @@
+using Blink
+using Base.Test
+
+@testset "content! Tests" begin
+    w = Window(Blink.@d(:show => false)); sleep(5.0)
+    body!(w, ""); sleep(1.0)  # body! is not synchronous.
+    @test (@js w document.querySelector("body").innerHTML) == ""
+
+    # Test reloading body and a selector element.
+    html = """<div id="a">hi world</div><div id="b">bye</div>"""
+    body!(w, html); sleep(1.0)
+    @test (@js w document.getElementById("a").innerHTML) == "hi world"
+    @test (@js w document.getElementById("b").innerHTML) == "bye"
+    content!(w, "div", "hello world"); sleep(1.0)
+    @test (@js w document.getElementById("a").innerHTML) == "hello world"
+    # TODO(nhdaly): Is this right? Should content!(w,"div",...) change _all_ divs?
+    @test (@js w document.getElementById("b").innerHTML) == "bye"
+
+    # Test `fade` parameter and scripts:
+    fadeTestHtml = """<script>var testJS = "test";</script><div id="d">hi world</div>"""
+    @testset "Fade True" begin
+        # Must create a new window to ensure javascript is reset.
+        w = Window(Blink.@d(:show => false)); sleep(5.0)
+
+        body!(w, fadeTestHtml; fade=true); sleep(1.0)
+        @test (@js w testJS) == "test"
+    end
+    @testset "Fade False" begin
+        # Must create a new window to ensure javascript is reset.
+        w = Window(Blink.@d(:show => false)); sleep(5.0)
+
+        body!(w, fadeTestHtml; fade=false); sleep(1.0)
+        @test (@js w testJS) == "test"
+    end
+end

test/runtests.jl

@@ -13,4 +13,6 @@ w = Window(Blink.@d(:show => false)); sleep(5.0)
 
 @test sprint(Blink.jsexpr, :(Dict("a" => 1, :b => 10))) == "{\"a\":1,b:10}"
 
+include("api.jl");
+
 cleanup && AtomShell.uninstall()