To manually test, drag 'Drag Me' to 'Drop Here' and drop. Several lines that say 'PASS' should appear below.

Drag Me
Drop Here
Drag handler: 
Legacy
DataTransferItemList
Drop handler: 
Legacy
DataTransferItemList

Tests drag'n drop and well as DataTransferItemList

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".

Running test with Legacy drag handler and Legacy drop handler
PASS testDataTransfer.types.length is 4
PASS testDataTransfer.types.indexOf("text/plain") >= 0 is true
PASS testDataTransfer.types.indexOf("text/uri-list") >= 0 is true
PASS testDataTransfer.types.indexOf("text/html") >= 0 is true
PASS testDataTransfer.types.indexOf("custom-data") >= 0 is true
PASS testDataTransfer.getData("text") is "sample"
PASS testDataTransfer.getData("url") is "http://www.google.com/"
PASS testDataTransfer.getData("text/html") is "<em>Markup</em>"
PASS testDataTransfer.getData("custom-data") is "hello world"
Running test with Legacy drag handler and DataTransferItemList drop handler
PASS testDataTransfer.items.length is 4
PASS testDataTransfer.items.add("test", "text/plain") is null
PASS testDataTransfer.items.length is 4
PASS JSON.stringify(expectedTypes) is JSON.stringify(types)
PASS testData is expectedTestData
PASS testData is expectedTestData
PASS testData is expectedTestData
PASS testData is expectedTestData
Running test with DataTransferItemList drag handler and Legacy drop handler
PASS testDataTransfer.items.add() threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': 1 argument required, but only 0 present..
PASS testDataTransfer.items.add(undefined) threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testDataTransfer.items.add("sample") threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testDataTransfer.items.add(null) threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testItem.kind is "string"
PASS testItem.type is "text/plain"
PASS testItem.kind is "string"
PASS testItem.type is "text/uri-list"
PASS testItem.kind is "string"
PASS testItem.type is "text/html"
PASS testItem.kind is "string"
PASS testItem.type is "custom-data"
PASS testDataTransfer.types.length is 4
PASS testDataTransfer.types.indexOf("text/plain") >= 0 is true
PASS testDataTransfer.types.indexOf("text/uri-list") >= 0 is true
PASS testDataTransfer.types.indexOf("text/html") >= 0 is true
PASS testDataTransfer.types.indexOf("custom-data") >= 0 is true
PASS testDataTransfer.getData("text") is "sample"
PASS testDataTransfer.getData("url") is "http://www.google.com/"
PASS testDataTransfer.getData("text/html") is "<em>Markup</em>"
PASS testDataTransfer.getData("custom-data") is "hello world"
Running test with DataTransferItemList drag handler and DataTransferItemList drop handler
PASS testDataTransfer.items.add() threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': 1 argument required, but only 0 present..
PASS testDataTransfer.items.add(undefined) threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testDataTransfer.items.add("sample") threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testDataTransfer.items.add(null) threw exception TypeError: Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'..
PASS testItem.kind is "string"
PASS testItem.type is "text/plain"
PASS testItem.kind is "string"
PASS testItem.type is "text/uri-list"
PASS testItem.kind is "string"
PASS testItem.type is "text/html"
PASS testItem.kind is "string"
PASS testItem.type is "custom-data"
PASS testDataTransfer.items.length is 4
PASS testDataTransfer.items.add("test", "text/plain") is null
PASS testDataTransfer.items.length is 4
PASS JSON.stringify(expectedTypes) is JSON.stringify(types)
PASS testData is expectedTestData
PASS testData is expectedTestData
PASS testData is expectedTestData
PASS testData is expectedTestData
PASS successfullyParsed is true

TEST COMPLETE