From 4787168aac1ff6a5ddb14755f221a28678106aaf Mon Sep 17 00:00:00 2001
From: Ryan Hartlage <2488333+ryanplusplus@users.noreply.github.com>
Date: Sun, 3 May 2026 08:53:26 -0400
Subject: [PATCH] Spec generators for grains, rotational-cipher, and space-age

---
 exercises/practice/grains/.meta/example.lua   |  3 +-
 .../practice/grains/.meta/spec_generator.lua  | 17 ++++
 exercises/practice/grains/grains_spec.lua     | 80 ++++++++++++-------
 .../.meta/spec_generator.lua                  | 10 +++
 .../rotational-cipher_spec.lua                | 22 ++---
 .../practice/space-age/.meta/example.lua      | 13 ++-
 .../space-age/.meta/spec_generator.lua        | 21 +++++
 exercises/practice/space-age/.meta/tests.toml |  1 -
 .../practice/space-age/space-age_spec.lua     | 51 ++++++------
 9 files changed, 143 insertions(+), 75 deletions(-)
 create mode 100644 exercises/practice/grains/.meta/spec_generator.lua
 create mode 100644 exercises/practice/rotational-cipher/.meta/spec_generator.lua
 create mode 100644 exercises/practice/space-age/.meta/spec_generator.lua

diff --git a/exercises/practice/grains/.meta/example.lua b/exercises/practice/grains/.meta/example.lua
index 1d42257a..4f716c84 100644
--- a/exercises/practice/grains/.meta/example.lua
+++ b/exercises/practice/grains/.meta/example.lua
@@ -1,11 +1,12 @@
 local grains = {}
 
 function grains.square(n)
+  assert(n >= 1 and n <= 64, 'square must be between 1 and 64')
   return 2 ^ (n - 1)
 end
 
 function grains.total()
-  return grains.square(65) - 1
+  return 2 ^ 64 - 1
 end
 
 return grains
diff --git a/exercises/practice/grains/.meta/spec_generator.lua b/exercises/practice/grains/.meta/spec_generator.lua
new file mode 100644
index 00000000..7034054c
--- /dev/null
+++ b/exercises/practice/grains/.meta/spec_generator.lua
@@ -0,0 +1,17 @@
+return {
+  module_name = 'grains',
+
+  generate_test = function(case)
+    if type(case.expected) == 'table' then
+      local template = [[
+        assert.has_error(function() grains.%s(%s) end, '%s')]]
+
+      return template:format(case.property, case.input and case.input.square or '', case.expected.error)
+    else
+      local template = [[
+        assert.are.equal(%s, grains.%s(%s))]]
+
+      return template:format(tostring(case.expected), case.property, case.input and case.input.square or '')
+    end
+  end
+}
diff --git a/exercises/practice/grains/grains_spec.lua b/exercises/practice/grains/grains_spec.lua
index 675070eb..0e568bf3 100644
--- a/exercises/practice/grains/grains_spec.lua
+++ b/exercises/practice/grains/grains_spec.lua
@@ -1,35 +1,55 @@
 local grains = require('grains')
 
 describe('grains', function()
-  it('square 1', function()
-    assert.are.equals(1, grains.square(1))
-  end)
-
-  it('square 2', function()
-    assert.are.equals(2, grains.square(2))
-  end)
-
-  it('square 3', function()
-    assert.are.equals(4, grains.square(3))
-  end)
-
-  it('square 4', function()
-    assert.are.equals(8, grains.square(4))
-  end)
-
-  it('square 16', function()
-    assert.are.equals(32768, grains.square(16))
-  end)
-
-  it('square 32', function()
-    assert.are.equals(2147483648, grains.square(32))
-  end)
-
-  it('square 64', function()
-    assert.are.equals(9223372036854775808, grains.square(64))
-  end)
-
-  it('total', function()
-    assert.are.equals(18446744073709551615, grains.total())
+  describe('returns the number of grains on the square', function()
+    it('grains on square 1', function()
+      assert.are.equal(1, grains.square(1))
+    end)
+
+    it('grains on square 2', function()
+      assert.are.equal(2, grains.square(2))
+    end)
+
+    it('grains on square 3', function()
+      assert.are.equal(4, grains.square(3))
+    end)
+
+    it('grains on square 4', function()
+      assert.are.equal(8, grains.square(4))
+    end)
+
+    it('grains on square 16', function()
+      assert.are.equal(32768, grains.square(16))
+    end)
+
+    it('grains on square 32', function()
+      assert.are.equal(2147483648, grains.square(32))
+    end)
+
+    it('grains on square 64', function()
+      assert.are.equal(9.2233720368547758e+18, grains.square(64))
+    end)
+
+    it('square 0 is invalid', function()
+      assert.has_error(function()
+        grains.square(0)
+      end, 'square must be between 1 and 64')
+    end)
+
+    it('negative square is invalid', function()
+      assert.has_error(function()
+        grains.square(-1)
+      end, 'square must be between 1 and 64')
+    end)
+
+    it('square greater than 64 is invalid', function()
+      assert.has_error(function()
+        grains.square(65)
+      end, 'square must be between 1 and 64')
+    end)
+  end)
+
+  it('returns the total number of grains on the board', function()
+    assert.are.equal(1.8446744073709552e+19, grains.total())
   end)
 end)
diff --git a/exercises/practice/rotational-cipher/.meta/spec_generator.lua b/exercises/practice/rotational-cipher/.meta/spec_generator.lua
new file mode 100644
index 00000000..18217bde
--- /dev/null
+++ b/exercises/practice/rotational-cipher/.meta/spec_generator.lua
@@ -0,0 +1,10 @@
+return {
+  module_name = 'rotational_cipher',
+
+  generate_test = function(case)
+    local template = [[
+      assert.are.equal("%s", rotational_cipher.%s("%s", %s))]]
+
+    return template:format(tostring(case.expected), case.property, case.input.text, case.input.shiftKey)
+  end
+}
diff --git a/exercises/practice/rotational-cipher/rotational-cipher_spec.lua b/exercises/practice/rotational-cipher/rotational-cipher_spec.lua
index bf09a78a..b930bfb7 100644
--- a/exercises/practice/rotational-cipher/rotational-cipher_spec.lua
+++ b/exercises/practice/rotational-cipher/rotational-cipher_spec.lua
@@ -2,43 +2,43 @@ local rotational_cipher = require('rotational-cipher')
 
 describe('rotational-cipher', function()
   it('rotate a by 0, same output as input', function()
-    assert.are.equal('a', rotational_cipher.rotate('a', 0))
+    assert.are.equal("a", rotational_cipher.rotate("a", 0))
   end)
 
   it('rotate a by 1', function()
-    assert.are.equal('b', rotational_cipher.rotate('a', 1))
+    assert.are.equal("b", rotational_cipher.rotate("a", 1))
   end)
 
   it('rotate a by 26, same output as input', function()
-    assert.are.equal('a', rotational_cipher.rotate('a', 26))
+    assert.are.equal("a", rotational_cipher.rotate("a", 26))
   end)
 
   it('rotate m by 13', function()
-    assert.are.equal('z', rotational_cipher.rotate('m', 13))
+    assert.are.equal("z", rotational_cipher.rotate("m", 13))
   end)
 
   it('rotate n by 13 with wrap around alphabet', function()
-    assert.are.equal('a', rotational_cipher.rotate('n', 13))
+    assert.are.equal("a", rotational_cipher.rotate("n", 13))
   end)
 
   it('rotate capital letters', function()
-    assert.are.equal('TRL', rotational_cipher.rotate('OMG', 5))
+    assert.are.equal("TRL", rotational_cipher.rotate("OMG", 5))
   end)
 
   it('rotate spaces', function()
-    assert.are.equal('T R L', rotational_cipher.rotate('O M G', 5))
+    assert.are.equal("T R L", rotational_cipher.rotate("O M G", 5))
   end)
 
   it('rotate numbers', function()
-    assert.are.equal('Xiwxmrk 1 2 3 xiwxmrk', rotational_cipher.rotate('Testing 1 2 3 testing', 4))
+    assert.are.equal("Xiwxmrk 1 2 3 xiwxmrk", rotational_cipher.rotate("Testing 1 2 3 testing", 4))
   end)
 
   it('rotate punctuation', function()
-    assert.are.equal('Gzo\'n zvo, Bmviyhv!', rotational_cipher.rotate('Let\'s eat, Grandma!', 21))
+    assert.are.equal("Gzo'n zvo, Bmviyhv!", rotational_cipher.rotate("Let's eat, Grandma!", 21))
   end)
 
   it('rotate all letters', function()
-    assert.are.equal('Gur dhvpx oebja sbk whzcf bire gur ynml qbt.',
-                     rotational_cipher.rotate('The quick brown fox jumps over the lazy dog.', 13))
+    assert.are.equal("Gur dhvpx oebja sbk whzcf bire gur ynml qbt.",
+                     rotational_cipher.rotate("The quick brown fox jumps over the lazy dog.", 13))
   end)
 end)
diff --git a/exercises/practice/space-age/.meta/example.lua b/exercises/practice/space-age/.meta/example.lua
index 7a24dd94..bd6e49d6 100644
--- a/exercises/practice/space-age/.meta/example.lua
+++ b/exercises/practice/space-age/.meta/example.lua
@@ -18,14 +18,19 @@ local function round(val, decimal)
 end
 
 function SpaceAge:new(seconds)
-  self.__index = self
-  local meta_tbl = { seconds = seconds }
+  local o = {}
   for k, v in pairs(SpaceAge.ORBITAL_PERIODS) do
     local val = round(seconds / SpaceAge.EARTH_ORBITAL_PERIOD / v, 2)
-    meta_tbl['on_' .. k] = load('return ' .. val)
+    o['on_' .. k] = load('return ' .. val)
   end
 
-  return setmetatable(meta_tbl, self)
+  return setmetatable(o, {
+    __index = function(_, key)
+      return function()
+        error('not a planet')
+      end
+    end
+  })
 end
 
 return SpaceAge
diff --git a/exercises/practice/space-age/.meta/spec_generator.lua b/exercises/practice/space-age/.meta/spec_generator.lua
new file mode 100644
index 00000000..61d66c94
--- /dev/null
+++ b/exercises/practice/space-age/.meta/spec_generator.lua
@@ -0,0 +1,21 @@
+return {
+  module_name = 'SpaceAge',
+
+  generate_test = function(case)
+    require'pl.pretty'.dump(case)
+
+    if type(case.expected) == 'table' then
+      local template = [[
+      local age = SpaceAge:new(%s)
+      assert.has_error(function() age.on_%s() end, '%s')]]
+
+      return template:format(tostring(case.input.seconds), case.input.planet:lower(), case.expected.error)
+    else
+      local template = [[
+        local age = SpaceAge:new(%s)
+        assert.are.equal(%s, age.on_%s())]]
+
+      return template:format(tostring(case.input.seconds), case.expected, case.input.planet:lower())
+    end
+  end
+}
diff --git a/exercises/practice/space-age/.meta/tests.toml b/exercises/practice/space-age/.meta/tests.toml
index a62017e4..7957bb77 100644
--- a/exercises/practice/space-age/.meta/tests.toml
+++ b/exercises/practice/space-age/.meta/tests.toml
@@ -35,4 +35,3 @@ description = "age on Neptune"
 
 [57b96e2a-1178-40b7-b34d-f3c9c34e4bf4]
 description = "invalid planet causes error"
-include = false
diff --git a/exercises/practice/space-age/space-age_spec.lua b/exercises/practice/space-age/space-age_spec.lua
index 1a324556..d5db3ba4 100644
--- a/exercises/practice/space-age/space-age_spec.lua
+++ b/exercises/practice/space-age/space-age_spec.lua
@@ -1,55 +1,50 @@
 local SpaceAge = require('space-age')
 
 describe('space-age', function()
-  it('age in seconds', function()
-    local age = SpaceAge:new(1000000)
-    assert.are.equal(1000000, age.seconds)
-  end)
-
-  it('age in Earth years', function()
+  it('age on earth', function()
     local age = SpaceAge:new(1000000000)
     assert.are.equal(31.69, age.on_earth())
   end)
 
-  it('age in Mercury years', function()
+  it('age on mercury', function()
     local age = SpaceAge:new(2134835688)
-    assert.are.equal(67.65, age.on_earth())
     assert.are.equal(280.88, age.on_mercury())
   end)
 
-  it('age in Venus years', function()
+  it('age on venus', function()
     local age = SpaceAge:new(189839836)
-    assert.are.equal(6.02, age.on_earth())
     assert.are.equal(9.78, age.on_venus())
   end)
 
-  it('age in Mars years', function()
-    local age = SpaceAge:new(2329871239)
-    assert.are.equal(73.83, age.on_earth())
-    assert.are.equal(39.25, age.on_mars())
+  it('age on mars', function()
+    local age = SpaceAge:new(2129871239)
+    assert.are.equal(35.88, age.on_mars())
   end)
 
-  it('age in Jupiter years', function()
+  it('age on jupiter', function()
     local age = SpaceAge:new(901876382)
-    assert.are.equal(28.58, age.on_earth())
     assert.are.equal(2.41, age.on_jupiter())
   end)
 
-  it('age in Saturn years', function()
-    local age = SpaceAge:new(3000000000)
-    assert.are.equal(95.06, age.on_earth())
-    assert.are.equal(3.23, age.on_saturn())
+  it('age on saturn', function()
+    local age = SpaceAge:new(2000000000)
+    assert.are.equal(2.15, age.on_saturn())
+  end)
+
+  it('age on uranus', function()
+    local age = SpaceAge:new(1210123456)
+    assert.are.equal(0.46, age.on_uranus())
   end)
 
-  it('age in Uranus years', function()
-    local age = SpaceAge:new(3210123456)
-    assert.are.equal(101.72, age.on_earth())
-    assert.are.equal(1.21, age.on_uranus())
+  it('age on neptune', function()
+    local age = SpaceAge:new(1821023456)
+    assert.are.equal(0.35, age.on_neptune())
   end)
 
-  it('age in Neptune year', function()
-    local age = SpaceAge:new(8210123456)
-    assert.are.equal(260.16, age.on_earth())
-    assert.are.equal(1.58, age.on_neptune())
+  it('invalid planet causes error', function()
+    local age = SpaceAge:new(680804807)
+    assert.has_error(function()
+      age.on_sun()
+    end, 'not a planet')
   end)
 end)