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When testing, it is sometimes useful to use a test double to manipulate or verify the behaviour of the system under test. The doubles are passed or injected into the class or method under test instead of instances of production code.

Destructuring is a pattern matching technique that is added to Javascript recently in EcmaScript 6. It allows you to bind a group of variables to a corresponding set of values when their pattern matches to the right hand-side and the left hand-side of the expression. let [x, y] = [1, 2] let ...

There are several unit testing tools for Python. This documentation topic describes the basic unittest module. Other testing tools include py.test and nosetests. This python documentation about testing compares several of these tools without going into depth.

Python makes regular expressions available through the re module. Regular expressions are combinations of characters that are interpreted as rules for matching substrings. For instance, the expression 'amount\D+\d+' will match any string composed by the word amount plus an integral number, separate...

SELECT column_name FROM table_name WHERE column_name operator value SELECT column_name, aggregate_function(column_name) FROM table_name GROUP BY column_name HAVING aggregate_function(column_name) operator value

svn copy [BRANCH-FROM-URL] [BRANCH-TO-URL] -m <COMMIT-LOG-MESSAGE> svn copy [^/PATH-TO-BRANCH-FROM] [^/PATH-TO-BRANCH-TO] -m <COMMIT-LOG-MESSAGE> As you might have noticed, we use svn copy command to create branches, tags and shelves (we'll skip mentioning tags and shel...

for {clauses} body for {clauses} yield body for (clauses) body for (clauses) yield body ParameterDetailsforRequired keyword to use a for loop/comprehensionclausesThe iteration and filters over which the for works.yieldUse this if you want to create or 'yield' a collection. Using yield wil...

var x int // declare variable x with type int var s string // declare variable s with type string x = 4 // define x value s = "foo" // define s value y := 5 // declare and define y inferring its type to int f := 4.5 // declare and define f inferring its type to float64 b := &quo...

ipairs(numeric_table) -- Lua table with numeric indices iterator pairs(input_table) -- generic Lua table iterator key, value = next(input_table, input_key) -- Lua table value selector table.insert(input_table, [position], value) -- insert specified value into the input table removed_value = ta...

A database snapshot is a read-only, static view of a SQL Server database which is transactionally consistent with the source database as of the moment of the snapshot's creation. A database snapshot always resides on the same server instance as its source database. As the source database is updat...

docker images [OPTIONS] [REPOSITORY[:TAG]] docker inspect [OPTIONS] CONTAINER|IMAGE [CONTAINER|IMAGE...] docker pull [OPTIONS] NAME[:TAG|@DIGEST] docker rmi [OPTIONS] IMAGE [IMAGE...] docker tag [OPTIONS] IMAGE[:TAG] [REGISTRYHOST/][USERNAME/]NAME[:TAG]

In MongoDB 3.0, MMAP (default) and WiredTiger are the stable storage engines. Usually, if your app is read-heavy, use MMAP. If its write-heavy, use WiredTiger. Your solution may also have a mixed replica set members where you can have one node configured with MMAP and another with WiredTiger. Yo...

  ![Alt text][id] ... intervening content ... [id]: /path/to/img.jpg "Optional title" The syntax for images is the same as that for links, but with an exclamation mark ! in front o...

ParameterDetailscharacter_expressionthe existing string in your datastart_positionthe position in character_expression to delete length and then insert the replacement_stringlengththe number of characters to delete from character_expressionreplacement_stringthe sequence of characters to insert in c...

Subroutines get their arguments to magic variable called @_. While it doesn't have to be unpacked, it's recommended, as it helps readability, and prevents accidental changes as arguments of @_ are passed by reference (can be modified).

While many scripts, icons, and stylesheets can be written straight into HTML markup, it is best practice and more efficient to include these resources in their own file and link them to your document. This topic covers linking external resources such as stylesheets and scripts into an HTML document....

ParameterDetails--pullEnsures that the base image (FROM) is up-to-date before building the rest of the Dockerfile.