The Testfor Commands:

For an Item Dropped:

/testfor @e[type=Item,id=] {Item:{id:"minecraft:",tag:{display:{Name:""}}}}

For Armor Worn:

Boots: /testfor @p {Inventory:[{Slot:100b,tag:{display:{Name:""}}}]}

Legs: /testfor @p {Inventory:[{Slot:101b,tag:{display:{Name:""}}}]}

Chest: /testfor @p {Inventory:[{Slot:102b,tag:{display:{Name:""}}}]}

Helm: /testfor @p {Inventory:[{Slot:103b,tag:{display:{Name:""}}}]}

For Item Held:

/testfor @p {SelectedItem:{id:minecraft:,tag:{display:{Name:""}}}}

For Item in Offhand:

/testfor @p {Inventory:[{Count:1b,Slot:-106b,Damage:0s,id:"minecraft:"}]}

For Item in 8th Slot:

/testfor @p {Inventory:[{Count:1b,Slot:8b,Damage:0s,id:"minecraft:"}]}

Targeting Commands

Radius: /testfor @e[r=1*]
*Radius of blocks

Amount of Entities: /testfor @e[c=3*]
*Amount of Entities

Player Mode: /testfor @a[m=1*]
*What mode a player is in

Tag: /testfor @e[tag=ExampleTag]

Score: /testfor @e[score_ExampleScore_min=1]
/testfor @e[score_ExampleScore=1]

Type: /testfor @e[type=enderman*]
*Type of mob

NOTE TO USERS THAT USE THESE COMMANDS:
The * in the commands are not a part of the command, just the variable. So when you use the commands, remove the * from the command if there is one.
I hope you find this helpful!

-Grim