Template Engine Kata

Write a "template engine" meaning a way to transform template strings, "Hello {$name}" into "instanced" strings. To do that a variable->value mapping must be provided. For example, if name="Pietro" and the template string is "Hello {$name}" the result would be "Hello Pietro".

Should evaluate template single variable expression

mapOfVariables.put("name","Pietro");
templateEngine.evaluate("Hello {$name}", mapOfVariables)

=> should evaluate to "Hello Pietro"

Should evaluate template with multiple expressions:

mapOfVariables.put("firstName","Pietro");
mapOfVariables.put("lastName","Di Bello");
templateEngine.evaluate("Hello {$firstName} ${lastName}", mapOfVariables);

=> should evaluate to "Hello Pietro Di Bello"

Should give error if template variable does not exist in the map:

map empty

templateEngine.evaluate("Hello {$firstName} ", mapOfVariables);

=> should throw MissingValueException

Should evaluate complex cases:

mapOfVariables.put("name","Pietro");
templateEngine.evaluate("Hello ${$name}}", mapOfVariables);

=> should evaluate to "Hello ${Pietro}"

Example origin is Koskela's book http://www.amazon.com/Test-Driven-Acceptance-Java-Developers/dp/1932394850