test: add initial tests for the State module

tests/plenary/state/state_spec.lua

@@ -0,0 +1,59 @@
+local utils = require('orgmode.utils')
+local state_mod = require('orgmode.state.state')
+local cache_path = vim.fs.normalize(vim.fn.stdpath('cache') .. '/org-cache.json', { expand_env = false })
+
+describe('State', function()
+  before_each(function()
+    -- Ensure the cache file is removed before each run
+    vim.fn.delete(cache_path, 'rf')
+  end)
+  it("should create a state file if it doesn't exist", function()
+    -- Ensure the file doesn't exist
+    local err, stat = pcall(vim.loop.fs_stat, cache_path)
+    if not err then
+      error('Cache file existed before it should! Ensure it is deleted before each test run!')
+    end
+
+    -- This creates the cache file on new instances of `State`
+    local state = state_mod()
+    state:load():finally(function()
+      ---@diagnostic disable-next-line: redefined-local
+      local err, stat = pcall(vim.loop.fs_stat, cache_path)
+      if err then
+        if type(stat) == 'string' and stat:match([[^ENOENT.*]]) then
+          error('Cache file did not exist')
+        end
+      end
+    end)
+  end)
+
+  it('should save the cache file as valid json', function()
+    local state = state_mod()
+    state:save():finally(function()
+      utils.readfile(cache_path, { raw = true }):next(function(cache_content)
+        local err, err_msg = vim.json.decode(cache_content, {
+          luanil = { object = true, array = true },
+        })
+
+        if err then
+          error('Cache file did not contain valid json after saving! Error: ' .. vim.inspect(err_msg))
+        end
+      end)
+    end)
+  end)
+
+  it('should be able to save and load state data', function()
+    local state = state_mod()
+
+    -- Set a variable into the state object
+    state.my_var = 'hello world'
+    state:save():finally(function()
+      -- "Wipe" the variable
+      state.my_var = nil
+      state:load():finally(function()
+        -- These should be the same after the wipe. We just loaded it back in from the state cache.
+        assert.are.equal(state.my_var, 'hello world')
+      end)
+    end)
+  end)
+end)