From 629bdf27b4a56d91491dc1b1cd2251ae4395d796 Mon Sep 17 00:00:00 2001
From: Jonathan Apodaca <jrapodaca@gmail.com>
Date: Sat, 11 Oct 2025 16:40:07 -0600
Subject: [PATCH] Renderer.mount: add tests

---
 lua/u/renderer.lua     |  7 ++++
 spec/renderer_spec.lua | 95 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/lua/u/renderer.lua b/lua/u/renderer.lua
index 3a9a13d..a10c0fe 100644
--- a/lua/u/renderer.lua
+++ b/lua/u/renderer.lua
@@ -60,6 +60,13 @@ function FnComponentContext:update(new_state)
   if self.on_change then vim.schedule(function() self.on_change() end) end
 end
 
+--- @private
+--- @param new_state TState
+function FnComponentContext:update_immediate(new_state)
+  self.state = new_state
+  if self.on_change then self.on_change() end
+end
+
 --- @alias u.renderer.FnComponent<TProps, TState> fun(ctx: u.renderer.FnComponentContext<TProps, TState>): u.renderer.Tree
 
 --- @class u.renderer.Tag
diff --git a/spec/renderer_spec.lua b/spec/renderer_spec.lua
index 5c4c670..891ce29 100644
--- a/spec/renderer_spec.lua
+++ b/spec/renderer_spec.lua
@@ -294,4 +294,99 @@ describe('Renderer', function()
       assert.are.same(bounds, { start = { 0, 9 }, stop = { 0, 19 } })
     end)
   end)
+
+  it('should mount and rerender components', function()
+    withbuf({}, function()
+      --- @type any
+      local leaked_state = { app = {}, c1 = {}, c2 = {} }
+
+      --- @param ctx u.renderer.FnComponentContext<any, { phase: string, count: integer }>
+      local function Counter(ctx)
+        if ctx.phase == 'mount' then ctx.state = { phase = ctx.phase, count = 1 } end
+        local state = assert(ctx.state)
+        state.phase = ctx.phase
+        leaked_state[ctx.props.id].ctx = ctx
+
+        return {
+          { 'Value: ', R.h.Number({}, tostring(state.count)) },
+        }
+      end
+
+      --- @param ctx u.renderer.FnComponentContext<any, {
+      ---   toggle1: boolean,
+      ---   show2: boolean
+      --- }>
+      function App(ctx)
+        if ctx.phase == 'mount' then ctx.state = { toggle1 = false, show2 = true } end
+        local state = assert(ctx.state)
+        leaked_state.app.ctx = ctx
+
+        return {
+          state.toggle1 and 'Toggle1' or R.h(Counter, { id = 'c1' }, {}),
+          '\n',
+
+          state.show2 and {
+            '\n',
+            R.h(Counter, { id = 'c2' }, {}),
+          },
+        }
+      end
+
+      local renderer = R.Renderer.new()
+      renderer:mount(R.h(App, {}, {}))
+
+      local Buffer = require 'u.buffer'
+      local buf = Buffer.current()
+      assert.are.same(buf:all():lines(), {
+        'Value: 1',
+        '',
+        'Value: 1',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'mount')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'mount')
+      leaked_state.app.ctx:update_immediate { toggle1 = true, show2 = true }
+      assert.are.same(buf:all():lines(), {
+        'Toggle1',
+        '',
+        'Value: 1',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'unmount')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'update')
+
+      leaked_state.app.ctx:update_immediate { toggle1 = true, show2 = false }
+      assert.are.same(buf:all():lines(), {
+        'Toggle1',
+        '',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'unmount')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'unmount')
+
+      leaked_state.app.ctx:update_immediate { toggle1 = false, show2 = true }
+      assert.are.same(buf:all():lines(), {
+        'Value: 1',
+        '',
+        'Value: 1',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'mount')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'mount')
+
+      leaked_state.c1.ctx:update_immediate { count = 2 }
+      assert.are.same(buf:all():lines(), {
+        'Value: 2',
+        '',
+        'Value: 1',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'update')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'update')
+
+      leaked_state.c2.ctx:update_immediate { count = 3 }
+      assert.are.same(buf:all():lines(), {
+        'Value: 2',
+        '',
+        'Value: 3',
+      })
+      assert.are.same(leaked_state.c1.ctx.state.phase, 'update')
+      assert.are.same(leaked_state.c2.ctx.state.phase, 'update')
+    end)
+  end)
 end)