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This is for compatibility testing of other Scratch implementations. First we test a bunch of blocks that expect strings. (Some of these take user input, since the only way to tell if they worked is by what shows up on the screen!) Then we test type casting in when doing equality comparison: "42" = 42, "TRue" = true, 1 = true, "TRue" != 1, and so on. Then we test a big "if / else" chain. This makes sure "true" (a string) and 1 (a number) are both treated as true (the boolean), and "false" and 0 are treated as false. Then we do some more complicated boolean logic tests, which make sure these values behave as expected when you use them in "not", "and", and "or". Then we test the addition operator. In some programming languages, the "+" character has two behaviors: to add two numbers, or to join (concatenate) two strings! Scratch always uses the "+" block for addition. Then we test the text operator blocks, such as "join", "letter of", "length of", and "contains?". These are all prone to being wonky or erroring in other programming languages if you aren't careful to treat the inputs as strings. Then we test indices in list and text blocks — item "3" of list should be the same as item 3 of list, for example! Last, we test that list operator blocks — "item # of thing in list" and "list contains thing?" — use the same comparison algorithm as the plain equality operator.
