defer delete strings in the tests in Two Fer (#191)

* `defer delete` strings in the tests in Two Fer

https://exercism.org/tracks/odin/exercises/two-fer

* use fmt.aprintf(), add memory management block into instructions.append.md

Author: 0riginaln0

exercises/practice/two-fer/.docs/instructions.append.md

@@ -66,6 +66,18 @@ If the arguments you need are in positional order, like in the example above, th
 greeting("John Doe", add_exclamation=true)
 ```
 
+## Memory management
+
+In this exercise you will implement a procedure which is meant to allocate the string it returns. Deallocating the string is the responsibility of the prodecure's caller.
+
+```odin
+// The procedure will be called like that:
+str := two_fer("Alice")
+// ...
+// and eventually the caller will delete the string
+delete(str)
+```
+
 ---
 
 You may also be interested in the official Odin documentation about [default arguments][default-values] and Odin [named arguments][named-arguments].

exercises/practice/two-fer/.meta/example.odin

@@ -3,5 +3,5 @@ package two_fer
 import "core:fmt"
 
 two_fer :: proc(name: string = "you") -> string {
-	return fmt.tprintf("One for {}, one for me.", name)
+	return fmt.aprintf("One for {}, one for me.", name)
 }

exercises/practice/two-fer/two_fer_test.odin

@@ -5,17 +5,23 @@ import "core:testing"
 @(test)
 /// description = no name given
 test_no_name_given :: proc(t: ^testing.T) {
-	testing.expect_value(t, two_fer(), "One for you, one for me.")
+	str := two_fer()
+	defer delete(str)
+	testing.expect_value(t, str, "One for you, one for me.")
 }
 
 @(test)
 /// description = a name given
 test_a_name_given :: proc(t: ^testing.T) {
-	testing.expect_value(t, two_fer("Alice"), "One for Alice, one for me.")
+	str := two_fer("Alice")
+	defer delete(str)
+	testing.expect_value(t, str, "One for Alice, one for me.")
 }
 
 @(test)
 /// description = another name given
 test_another_name_given :: proc(t: ^testing.T) {
-	testing.expect_value(t, two_fer("Bob"), "One for Bob, one for me.")
+	str := two_fer("Bob")
+	defer delete(str)
+	testing.expect_value(t, str, "One for Bob, one for me.")
 }