Add test file

Correspondingly, add the generated "tags" file to .gitignore.
I tried to add "actual code" and have too many tests rather than only
complex ones.
Surely, some cases are not covered. For example, using multiple macros
for a definition.

Author: janEbert

.gitignore

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+tags
+

testfile.jl

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+module CtagsTest
+
+using Test
+using Base.Sort.QuickSort
+using Base.Sort: MergeSort, InsertionSort
+
+#=
+using Documenter
+=#
+
+import Distributed
+import Base.show
+import DelimitedFiles: readdlm, writedlm
+
+struct ImmutablePoint{T}
+    x::T
+    y::T
+end
+
+mutable struct MutablePoint{T}
+    x::T
+    y::T
+end
+
+"""
+    Names(first, last)
+
+Contains the first and last name of a person.
+Can be called with keywords.
+
+# Example
+
+```julia-repl
+julia> Names(last="Bond", first="James") # Bond
+Names("James", "Bond")
+```
+"""
+Base.@kwdef struct Names
+    first::AbstractString
+    last::AbstractString
+end
+
+"""
+    Names(first, last)
+
+Contains the first and last name of a person.
+Can be called with keywords.
+
+# Examples
+```jldoctest
+julia> Names(last="Bond", first="James") # Bond
+Names("James", "Bond")
+```
+"""
+Base.@kwdef mutable struct VariableNames
+    first::AbstractString
+    last::AbstractString
+end
+
+# Lambda function
+"""
+    returnsquarepower()
+
+Return the power used to square numbers.
+
+# Examples
+```jldoctest; output = false
+mysquarepower = returnsquarepower()
+# or
+const myconstsquarepower = returnsquarepower()
+
+# output
+
+2
+```
+"""
+returnsquarepower = () -> 2
+
+#=
+deprecated_returnsquarepower() = 2.0
+const deprecated_squarepower = deprecated_returnsquarepower()
+=#
+
+"Number used to square – not cube – numbers."
+squarepower = returnsquarepower
+"A universally accepted greeting."
+const greeting = "Hello"
+
+function square(x)
+    x ^ squarepower
+end
+
+function addone!(x::T) where {T <: Number}
+    x += one(T)
+end
+
+addtwo!(x::T) where {T <: Number} = (x += one(T) + one(T))
+
+addcoment(string::AbstractString, comment, spaces=1) = begin  # Maybe write without `begin`?
+    string * " "^spaces * "# " * comment
+end
+
+multiply(x, y) = x * y
+multiply(x, y...) = begin
+    multiply(y...) * x
+end
+
+"""
+    greet(x)
+
+Generate different greeting strings depending on who you are talking to.
+
+# Examples
+```@meta
+DocTestSetup = quote
+    function printgreeting(x)
+        println(greet(x))
+    end
+end
+```
+
+```jldoctest
+julia> greet("Julia")
+Hello Julia!
+
+julia> greet(3141)
+Hello Robot 3141!
+
+julia> greet(0x1f)
+Hello Robot 0x1f!
+
+julia> greet(BitVector([1, 0, 1]))
+Hello binary data 101!
+```
+"""
+@generated function greet(x)
+    if x <: Union{AbstractString, AbstractChar}
+        :("$greeting $x!")
+    elseif x <: Unsigned
+        :("$greeting Robot 0x$(string(x, base=16))!")
+    elseif x <: Number
+        :("$greeting Robot $(string(x))!")
+    else
+        :("$greeting binary data $(bitstring(x))!")
+    end
+end
+
+# TODO add `greet` for aliens
+
+greet("Julia")
+
+end # module
+