- title:    string interpolation
  context:  {key: 'world', num: 1}
  template: {message: 'hello ${key}', 'k-${num}': true}
  output:   {message: 'hello world', 'k-1': true}

#- title:    string interpolation with object evaluation
#  context:  {key: 'world', num: 1}
#  template: {message: 'hello ${{a: "world"}.a}', 'k-${{a: 1}.a + {a: 0}.a}': true}
#  output:   {message: 'hello world', 'k-1': true}

- title: multiple string interpolation (1)
  context:  {a: 'hello', b: 'world'}
  template: {message: '${a} ${b}'}
  output:   {message: 'hello world'}

- title: multiple string interpolation (2)
  context:  {a: 'hello', b: 'world'}
  template: {message: '${a}$$${b}'}
  output:   {message: 'hello$${b}'}

- title: multiple string interpolation (3)
  context:  {a: 'hello', b: 'world'}
  template: {message: '${a}##${b}'}
  output:   {message: 'hello##world'}

- title: string interpolation escapes
  context:  {}
  template: {message: 'a literal $${in a string}'}
  output:   {message: 'a literal ${in a string}'}

- title: string interpolation escapes with more $
  context:  {x: 'a'}
  template: ['${x}', '$${x}', '$$${x}', '$$$${x}', '$$$$${x}']
  output:   ['a', '${x}', '$${x}', '$$${x}', '$$$${x}']

- title: string interpolation of keys
  context: {name: 'foo', value: 'bar'}
  template: {"tc_${name}": "${value}"}
  output: {"tc_foo": "bar"}

#- title: string interpolation with unbalanced }
#  context:  {}
#  template: {message: 'tricky ${"}}}}"}'}
#  output:   {message: 'tricky }}}}'}

- title:    can't interpolate arrays
  context:  {key: [1,2,3]}
  template: {message: 'hello ${key}'}
  error:
    message: "'key' cannot be interpolated into a string: [1, 2, 3]"

- title:    can't interpolate objects
  context:  {key: {}}
  template: 'hello ${key}'
  error:
    message: "'key' cannot be interpolated into a string: {}"

- title:    booleans interpolate
  context:  {t: true, f: false}
  template: '${t} or ${f}: yeast is a bacterium'
  output:   'true or false: yeast is a bacterium'

- title:    numbers interpolate
  context:  {round: 3, decimal: 3.75}
  template: '${round}, really ${decimal}'
  output:   '3, really 3.75'

- title:    nulls interpolate
  context:  {nothing: null}
  template: 'big pile of ${nothing}'
  output:   'big pile of '