diff --git a/docs/api/strict-mode.md b/docs/api/strict-mode.md
index f5ca78a..d69b527 100644
--- a/docs/api/strict-mode.md
+++ b/docs/api/strict-mode.md
@@ -15,10 +15,10 @@ vide.strict = true
 
 What strict mode will do:
 
-1. Run derived callbacks twice when re-evaluating.
-2. Run watcher callbacks twice when a state changes.
+1. Run derived sources twice a source updates.
+2. Run watchers twice when a source updates.
 3. Throw an error if yields occur where they are not allowed.
-4. Checks for `map()` returning primitive values.
+4. Checks for `indexes()` and `values()` returning primitive values.
 5. Better error reporting and stack traces.
 
 It is recommend to develop UI with strict mode and to disable it when pushing to
diff --git a/src/bind.luau b/src/bind.luau
index 4a36a34..d136697 100644
--- a/src/bind.luau
+++ b/src/bind.luau
@@ -43,7 +43,7 @@ function setup(instance: Instance, setter: (Instance) -> ())
         local trace = traceback()
         setter = function(instance)
             local ok, err: string? = pcall(fn, instance)
-            if not ok then warn(`error occured updating state binding:\n{err}\nset from:{trace}`) end
+            if not ok then warn(`error occured updating property:\n{err}\nset from:{trace}`) end
         end
     end
 
@@ -68,8 +68,6 @@ function setup(instance: Instance, setter: (Instance) -> ())
     instance:GetPropertyChangedSignal("Parent"):Connect(ref)
 end
 
--- todo: move `fn` as arg?
-
 local function bind_property(instance: Instance, property: string, fn: () -> unknown)
     setup(instance, function(instance_weak: any)
         instance_weak[property] = fn()
@@ -80,13 +78,13 @@ local function bind_parent(instance: Instance, fn: () -> Instance?)
     instance.Destroying:Connect(function()
         instance= nil :: any -- allow gc when destroyed
     end)
+
     setup(instance, function(instance)
         local _ = instance -- state will strongly reference instance when parent is bound
         instance.Parent = fn()    
     end)
 end
 
--- todo: could optimize, see: maps.luau values()
 local function bind_children(parent: Instance, fn: () -> { Instance })
     local current_child_set: { [Instance]: true } = {} -- cache of all children parented before update
     local new_child_set: { [Instance]: true } = {} -- cache of all children parented after update
diff --git a/src/create.luau b/src/create.luau
index 06ded51..3c3ed71 100644
--- a/src/create.luau
+++ b/src/create.luau
@@ -12,7 +12,7 @@ local defaults = require(script.Parent.defaults)
 local apply = require(script.Parent.apply)
 local memoize = require(script.Parent.memoize)
 
-local function createInstance(className: string)
+local function create_instance(className: string)
     local success, instance: Instance = pcall(Instance.new, className :: any)
     if success == false then throw(`invalid class name, could not create instance of class { className }`) end
 
@@ -26,9 +26,9 @@ local function createInstance(className: string)
     return function(properties: { [any]: unknown }): Instance
         return apply(instance:Clone(), properties)    
     end  
-end; createInstance = memoize(createInstance)
+end; create_instance = memoize(create_instance)
 
-local function cloneInstance(instance: Instance)
+local function clone_instance(instance: Instance)
     return function(properties: { [any]: unknown }): Instance
         local clone = instance:Clone()
         if not clone then error("Attempt to clone a non-archivable instance", 3) end
@@ -38,9 +38,9 @@ end
 
 local function create(classNameOrInstance: string|Instance)
     if type(classNameOrInstance) == "string" then
-        return createInstance(classNameOrInstance)
+        return create_instance(classNameOrInstance)
     elseif typeof(classNameOrInstance) == "Instance" then
-        return cloneInstance(classNameOrInstance)
+        return clone_instance(classNameOrInstance)
     else
         error("Bad argument #1, expected string or instance, got "..typeof(classNameOrInstance), 2)
     end
diff --git a/src/graph.luau b/src/graph.luau
index 60e1158..168d8e3 100644
--- a/src/graph.luau
+++ b/src/graph.luau
@@ -1,5 +1,6 @@
 if not game then script = require "test/wrap-require" end
 
+local throw = require(script.Parent.throw)
 local flags = require(script.Parent.flags)
 
 export type Node<T> = {
@@ -13,28 +14,30 @@ local reff = false
 local refs = {} :: { Node<unknown> }
 
 local WEAK_VALUES_RESIZABLE = { __mode = "vs" }
-local EVALUATION_ERR = "error while evaluating node:\n\n"
+local EVALUATION_ERR = "error while evaluating source:\n\n"
 
 setmetatable(refs :: any, WEAK_VALUES_RESIZABLE)
 
-local check_for_yield do
+local check_for_yield: <T...>(fn: (T...) -> unknown, T...) -> () do
     local t = { __mode = "kv" }
     setmetatable(t, t)
 
-    check_for_yield = function<T..., U...>(fn: (T...) -> (), ...: any)
+    check_for_yield = function(fn, ...: any)
         local args = { ... }
-        t.__unm = function()
+
+        t.__unm = function(_)
             fn(unpack(args))
         end
+
         local ok, err = pcall(function()
-            return -t :: any
+            local _ = -t
         end)
 
         if not ok then
             if err == "attempt to yield across metamethod/C-call boundary" or err == "thread is not yieldable" then
-                error(EVALUATION_ERR .. "cannot yield when deriving node in watcher", 3)
+                throw(EVALUATION_ERR .. "cannot yield when deriving node in watcher")
             else
-                error(EVALUATION_ERR..err, 3)
+                throw(EVALUATION_ERR .. err)
             end
         end
     end
@@ -45,10 +48,16 @@ local function set_effect<T>(node: Node<unknown>, fn: (T) -> (), key: T)
 end
 
 local function run_effects(node: Node<unknown>)
-    for effect, key in next, node.effects do
-        if flags.strict then effect(key) end
-        effect(key)
-    end 
+    if flags.strict then
+        for effect, key in next, node.effects do
+            effect(key)
+            effect(key)
+        end
+    else
+        for effect, key in next, node.effects do
+            effect(key)
+        end
+    end
 end
 
 -- retrieves a node's cached value
@@ -71,8 +80,10 @@ end
 local function update(node: Node<unknown>)
     run_effects(node)
     if node.children then
+        local strict = flags.strict
+
         for _, child in node.children do
-            if flags.strict then check_for_yield(child.derive) end
+            if strict then check_for_yield(child.derive) end
             child.cache = child.derive()
             update(child)
         end
@@ -108,7 +119,7 @@ local function capture<T, U>(fn: (U?) -> T, arg: U?): ({ Node<unknown> }, T)
 
     reff = false
 
-    if not ok then error("error while detecting watcher: " .. result :: string, 0) end
+    if not ok then throw(EVALUATION_ERR .. result :: string) end
 
     return refs, result :: T
 end
diff --git a/src/init.luau b/src/init.luau
index cabd2f2..8192958 100644
--- a/src/init.luau
+++ b/src/init.luau
@@ -14,6 +14,7 @@ local indexes, values = require(script.maps)()
 local spring, update_springs = require(script.spring)()
 local action = require(script.action)()
 
+local throw = require(script.throw)
 local flags = require(script.flags)
 
 local vide = {
@@ -49,15 +50,20 @@ local vide = {
 }
 
 setmetatable(vide :: any, {
-    __index = function(_, index: unknown)
-        error(string.format("\"%s\" is not a valid member of vide", tostring(index)), 2)
+    __index = function(_, index: unknown): ()
+        if index == "strict" then
+            return flags.strict
+        else
+            throw(`{tostring(index)} is not a valid member of vide`)
+        end
     end,
 
     __newindex = function(_, index: unknown, value: unknown)
         if index == "strict" then
-            flags.strict = if type(value) == "boolean" then value else error("strict must be a boolean", 2)
+            if value ~= true then throw "strict mode can only be set to true" end
+            flags.strict = true
         else
-            error(string.format("\"%s\" is not a valid member of vide", tostring(index)), 2)
+            throw(`{tostring(index)} is not a valid member of vide`)
         end
     end
 })
diff --git a/src/maps.luau b/src/maps.luau
index 553b495..fe6f8be 100644
--- a/src/maps.luau
+++ b/src/maps.luau
@@ -1,5 +1,7 @@
 if not game then script = require "test/wrap-require" end
 
+local throw = require(script.Parent.throw)
+local flags = require(script.Parent.flags)
 local graph = require(script.Parent.graph)
 type Node<T> = graph.Node<T>
 local create = graph.create
@@ -9,6 +11,15 @@ local link = graph.link
 
 type Map<K, V> = { [K]: V }
 
+local function check_primitives(t: {})
+    if not flags.strict then return end
+
+    for _, v in next, t do
+        if type(v) == "table" or type(v) == "userdata" then continue end
+        throw("table source map cannot return primitives")
+    end
+end
+
 -- todo: optimize output array
 local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI, K) -> VO): () -> { VO }
     local input_cache = {} :: Map<K, VI>
@@ -54,7 +65,8 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
         for _, v in next, output_cache do
             table.insert(output_array, v)
         end
-
+        check_primitives(output_array)
+        
         return output_array
     end
 
@@ -86,6 +98,16 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
 
     local function recompute(data: Map<K, VI>)
         local cur_input_cache, new_input_cache = cur_input_cache_up, new_input_cache_up
+
+        if flags.strict then
+            local cache = {}
+            for _, v in next, data do
+                if cache[v] ~= nil then
+                    throw "duplicate table value detected"
+                end
+                cache[v] = true
+            end
+        end
     
         -- process data
         for i, v in next, data do
@@ -136,6 +158,7 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
     for _, node in next, nodes do
         link(node, output, derive)
     end
+    check_primitives(output_array)
 
     output.cache = recompute(value)
 
diff --git a/src/spring.luau b/src/spring.luau
index 2326e51..b5f573c 100644
--- a/src/spring.luau
+++ b/src/spring.luau
@@ -157,7 +157,7 @@ local function update_springs(dt: number)
                 typeof(initial_position),
                 target_type
             ))
-            throw(`Cannot tween type { typeof(initial_position) } and { target_type }`)
+            throw(`cannot tween type { typeof(initial_position) } and { target_type }`)
             continue
         end
 
@@ -165,14 +165,13 @@ local function update_springs(dt: number)
 
         if lerp == nil then 
             springs[data] = nil
-            throw(`Cannot animate type { target_type }`)
+            throw(`cannot animate type { target_type }`)
             continue
         end
 
         local new_time = data.duration + dt
         local new_alpha = solve(data.period, data.damping_ratio, data.initial_velocity, new_time)
         local new_velocity = -(new_alpha - data.alpha)/dt
-
         local acceleration = (new_velocity - data.velocity)/dt
 
         data.velocity = new_velocity
@@ -181,7 +180,8 @@ local function update_springs(dt: number)
 
         local value = lerp(initial_position, target_position, new_alpha)
 
-        if math.abs(acceleration) < 0.01 then
+        if math.abs(acceleration) < (0.01 / data.period) then
+            -- close enough to target, remove and set value to target
             table.insert(remove_queue, data)
             set(output, target_position)
         else
diff --git a/test/benchmark.luau b/test/benchmark.luau
index 1ea533e..f9bc37a 100644
--- a/test/benchmark.luau
+++ b/test/benchmark.luau
@@ -1,14 +1,10 @@
-------------------------------------------------------------------------------------------
--- benchmark.lua
-------------------------------------------------------------------------------------------
-
 local BENCH, START = require("test/testkit").benchmark()
 
 local vide = require "src/init"
 
 local N = 2^18 -- 262144
 
-BENCH("Create state", function()
+BENCH("create state", function()
     local cache = table.create(N)
     local source = vide.source
 
@@ -17,7 +13,7 @@ BENCH("Create state", function()
     end
 end)
 
-BENCH("Get value", function()
+BENCH("get value", function()
     local state = vide.source(1)
 
     for i = 1, START(N) do
@@ -25,7 +21,7 @@ BENCH("Get value", function()
     end
 end)
 
-BENCH("Set value", function()
+BENCH("set value", function()
     local state = vide.source(1)
 
     for i = 1, START(N) do
@@ -33,7 +29,7 @@ BENCH("Set value", function()
     end
 end)
 
-BENCH("Derive 1 state", function()
+BENCH("derive 1 state", function()
     local cache = table.create(N)
     local state = vide.source(1)
     local derive = vide.derive
@@ -45,7 +41,7 @@ BENCH("Derive 1 state", function()
     end
 end)
 
-BENCH("Derive 4 states", function()
+BENCH("derive 4 states", function()
     local cache = table.create(N)
     local state = vide.source(1)
     local state2 = vide.source(2)
@@ -60,7 +56,7 @@ BENCH("Derive 4 states", function()
     end
 end)
 
-BENCH("Set derived value", function()
+BENCH("set derived value", function()
     local state = vide.source(1)
     local _derived = vide.derive(state)
 
@@ -69,7 +65,7 @@ BENCH("Set derived value", function()
     end
 end)
 
-BENCH("Apply 0 properties", function()
+BENCH("apply 0 properties", function()
     local apply = require "src/apply"
     local instance = vide.create("Frame") {}
 
@@ -78,7 +74,7 @@ BENCH("Apply 0 properties", function()
     end
 end)
 
-BENCH("Apply 8 properties", function()
+BENCH("apply 8 properties", function()
     local apply = require "src/apply"
     local instance = vide.create("Frame") {}
 
@@ -96,7 +92,7 @@ BENCH("Apply 8 properties", function()
     end
 end)
 
-BENCH("Bind state", function()
+BENCH("bind source", function()
     local apply = require "src/apply"
     local instance = vide.create("Frame") {}
     local state = vide.source(1)
@@ -108,7 +104,7 @@ BENCH("Bind state", function()
     end
 end)
 
-BENCH("Update binding", function()
+BENCH("update binding", function()
     local apply = require "src/apply"
     local instance = vide.create("Frame") {}
     local state = vide.source(1)
diff --git a/test/tests.luau b/test/tests.luau
index 1de2f7e..068d33b 100644
--- a/test/tests.luau
+++ b/test/tests.luau
@@ -1,13 +1,11 @@
 local testkit = require("test/testkit")
-local TEST, CASE, CHECK, FINISH, SKIP = testkit.test()
+local TEST, CASE, CHECK, FINISH = testkit.test()
 
 local mock = require "test/mock"
-
 local Instance, Signal = mock.Instance, mock.Signal
 
 local vide = require "src/init"
 
--- force run garbage collector cycles
 local function gc(n: number?)
     for i = 1, n or 3 do
         (collectgarbage :: any)("collect")
@@ -29,12 +27,12 @@ TEST("graph", function()
     local link = graph.link
     local set_effect = graph.set_effect
 
-    do CASE "Node creation"
+    do CASE "node creation"
         local node = create(1)
         CHECK(get(node) == 1)
     end
 
-    do CASE "Node value"
+    do CASE "node value"
         local node = create(0)
         set(node, 1)
         CHECK(get(node) == 1)
@@ -42,7 +40,7 @@ TEST("graph", function()
         CHECK(get(node) == 2)
     end
 
-    do CASE "Capture nodes"
+    do CASE "capture nodes"
         local node1 = create(nil)
         local node2 = create(nil)
         local nodes = capture(function()
@@ -52,7 +50,7 @@ TEST("graph", function()
         CHECK(nodes[2] == node2)
     end
 
-    do CASE "Linking nodes"
+    do CASE "linking nodes"
         local parent = create(1)
         local child = create(0)
 
@@ -64,7 +62,7 @@ TEST("graph", function()
         CHECK(get(child) == 2) -- child should automatically update
     end
 
-    do CASE "Capture and link nodes"
+    do CASE "capture and link nodes"
         local parent = create(1)
         local child = create()
 
@@ -76,38 +74,13 @@ TEST("graph", function()
         CHECK(get(child) == "2")
     end
 
-    --[[
-    do CASE "Scoped captures"
-        local a = create(0)
-        local b = create(nil :: any)
-
-        local count = 0
-        
-        b.cache = capture_and_link(b, function()
-            count += 1
-            local data = get(a)
-            local c = create(data)
-            get(c)
-            return c
-        end)
-
-        local c = get(b)
-
-        CHECK(count == 1)
-        set(c, 1)
-        CHECK(count == 1)
-        set(a, 1)
-        CHECK(count == 2)
-    end
-    ]]
-
-    do CASE "Nodes garbage collection"
+    do CASE "nodes garbage collection"
         local wref = weak { create(1) }
         gc()
         CHECK(not wref[1])
     end
 
-    do CASE "Node effect garbage collection"
+    do CASE "node effect garbage collection"
         do
             local wref
 
@@ -179,18 +152,18 @@ TEST("source()", function()
     local source = vide.source
     local watch = vide.watch
 
-    do CASE "Create source"
+    do CASE "create source"
         local state = source(1)
         CHECK(state() == 1)
     end
 
-    do CASE "Set and get source value"
+    do CASE "set and get source value"
         local state = source(1)
         state(2)
         CHECK(state() == 2)
     end
 
-    do CASE "Does not update if same value"
+    do CASE "does not update if same value"
         local state = source(1)
 
         local updates = -1
@@ -206,7 +179,7 @@ TEST("source()", function()
         CHECK(updates == 1)
     end
 
-    do CASE "Does update if same value is table"
+    do CASE "does update if same value is table"
         local state = source {}
 
         local updates = -1
@@ -225,7 +198,7 @@ TEST("derive()", function()
     local source = vide.source
     local derive = vide.derive
 
-    do CASE "Derive new value on source change"
+    do CASE "derive new value on source change"
         local inputA = source(1)
         local inputB = source(2)
 
@@ -238,7 +211,7 @@ TEST("derive()", function()
         CHECK(output() == "4")
     end
 
-    do CASE "Derive transformed source"
+    do CASE "derive wrapped source"
         local input = source(1)
 
         local transform = function()
@@ -254,25 +227,7 @@ TEST("derive()", function()
         CHECK(output() == 2)
     end
 
-    --[[
-    do CASE "Cleanup"
-        local count, set = source(1)
-
-        local derived = derive(function(from)
-            return { Value = from(count), Destroyed = false }
-        end, function(v)
-            v.Destroyed = true
-        end)
-
-        local first = derived()
-        CHECK(first.Destroyed == false)
-        set(2)
-        local _ = derived() -- trigger recalc
-        CHECK(first.Destroyed == true)
-    end
-    ]]
-
-    do CASE "Garbage collection"
+    do CASE "garbage collection"
         do -- check that `b` does not allow gc of `a`
             local wref, b
             
@@ -309,7 +264,7 @@ TEST("derive()", function()
         end
     end
 
-    do CASE "Garbage collection 2"
+    do CASE "garbage collection 2"
         -- creats a chain `a -> b -> c` where `a` is the source
         local function setup()
             local a = source(0)
@@ -362,7 +317,7 @@ TEST("watch()", function()
     local watch = vide.watch
     local cleanup = vide.cleanup
 
-    do CASE "Capture states"
+    do CASE "capture sourcess"
         local a = source(1)
         local b = source(1)
 
@@ -380,7 +335,7 @@ TEST("watch()", function()
         CHECK(runcount == 2)
     end
 
-    do CASE "Stop watch"
+    do CASE "stop watch"
         local a = source(1)
 
         local runcount = -1
@@ -394,7 +349,7 @@ TEST("watch()", function()
         CHECK(runcount == 0)
     end
 
-    do CASE "Side-effect cleanup"
+    do CASE "side-effect cleanup"
         local state = source(1)
 
         local effect_runcount = 0
@@ -421,7 +376,7 @@ TEST("watch()", function()
         CHECK(cleanup_runcount == 2)
     end
 
-    do CASE "Garbage collection"
+    do CASE "garbage collection"
         local function factory(p)
             return function()
                 p()
@@ -486,7 +441,7 @@ TEST("cleanup()", function()
     local watch = vide.watch
     local cleanup = vide.cleanup
 
-    do CASE "Cleanup runs for watcher"
+    do CASE "cleanup runs for watcher"
         local state = source(1)
 
         local watched = 0
@@ -520,7 +475,7 @@ TEST("cleanup()", function()
         CHECK(cleaned == 2)
     end
 
-    do CASE "Scoped"
+    do CASE "scoped"
         local function setup()
             local state = source(1)
             local obj = { cleaned = 0 }
@@ -562,7 +517,7 @@ TEST("cleanup()", function()
         CHECK(objB.cleaned == 2)
     end
 
-    do CASE "Multiple cleanup"
+    do CASE "multiple cleanup"
         local state = source(1)
 
         local queue = {}
@@ -595,14 +550,14 @@ TEST("create()", function()
     local create = vide.create
     local source = vide.source
 
-    do CASE "Apply default properties"
+    do CASE "apply default properties"
         local defaults = require("src/defaults")
         local frame = create "Frame" {} :: Instance & { BorderSizePixel: any, BorderColor3: any }
         CHECK(frame.BorderSizePixel == defaults.Frame.BorderSizePixel)
         CHECK(frame.BorderColor3 == defaults.Frame.BorderColor3)
     end
 
-    do CASE "Set properties"
+    do CASE "set properties"
         local text = create "TextLabel" {
             Name = "Label",
             Text = "test"
@@ -611,7 +566,7 @@ TEST("create()", function()
         CHECK(text.Text == "test")
     end
 
-    do CASE "Set nested properties"
+    do CASE "set nested properties"
         local text = create "TextLabel" {
             { Name = "Label" },
             Group = { Text = "test" }
@@ -620,12 +575,12 @@ TEST("create()", function()
         CHECK(text.Text == "test")
     end
 
-    do CASE "Independent"
+    do CASE "independent"
         local frame = create "Frame"
         CHECK(frame {} ~= frame {})
     end
 
-    do CASE "Set children"
+    do CASE "set children"
         local frame = create "Frame" {
             create "TextLabel" { Name = "A" },
             create "TextLabel" { Name = "B" },
@@ -652,7 +607,7 @@ TEST("create()", function()
         CHECK(frame:FindFirstChild "G")
     end
 
-    do CASE "Binding properties to state"
+    do CASE "binding properties to source"
         local name = source("Hi")
         local text = source("Bye")
 
@@ -671,7 +626,7 @@ TEST("create()", function()
         CHECK(label.Text == "Bar")
     end
 
-    do CASE "Binding garbage collection"
+    do CASE "binding garbage collection"
         do -- instance should gc when unparented
             local state = source("Hi")
 
@@ -774,7 +729,7 @@ TEST("create()", function()
         end
     end
 
-    do CASE "Bind same state to multiple instance properties"
+    do CASE "bind same state to multiple instance properties"
         local state = source "1"
 
         local text = create "TextBox" {
@@ -790,7 +745,7 @@ TEST("create()", function()
         CHECK(text.PlaceholderText == "2")
     end
 
-    do CASE "Bind children"
+    do CASE "bind children"
         local state = source()
 
         local a, b, c = 
@@ -844,7 +799,7 @@ TEST("create()", function()
     end
     ]]
 
-    do CASE "GC test"
+    do CASE "garbage collection test"
         local wref
 
         do
@@ -871,13 +826,11 @@ TEST("create()", function()
     end
 end)
 
--- todo: more comprehensive tests for maps
-
 TEST("indexes()", function()
     local source = vide.source
     local indexes = vide.indexes
 
-    do CASE "Use state"
+    do CASE "use source"
         local input = source { 1, 2, 3 }
 
         local output = indexes(input, function(v, k)
@@ -889,7 +842,7 @@ TEST("indexes()", function()
         CHECK("" .. input()[3] == output()[3])
     end
 
-    do CASE "Cache result"
+    do CASE "cache result"
         local input = source { 1, 2, 3 }
 
         local runcount = table.create(3, 0)
@@ -910,7 +863,7 @@ TEST("indexes()", function()
         CHECK(runcount[3] == 1)
     end
 
-    do CASE "Removal reflected"
+    do CASE "removal reflected"
         local input = source { 1, 2, 3 }
 
         local output = indexes(input, function(v, i)
@@ -926,95 +879,44 @@ TEST("indexes()", function()
         CHECK(t[3] == nil)
     end
 
---[[
-    do CASE "Bind children"
-        local state, set = source { "A", "B", "C" }
-
-        local derived = map(state, function(i, v)
-            return create "TextLabel" {
-                Name = v,
-                Text = tostring(i)
-            }
-        end)
-
-        local frame = create "Frame" {
-            Name = "21",
-            [Children] = derived
-        }
-
-        local function find(childname: string): TextLabel
-            return frame:FindFirstChild(childname) :: TextLabel
-        end
-
-        CHECK(find "A".Text == "1")
-        CHECK(find "B".Text == "2")
-        CHECK(find "C".Text == "3")
+    do CASE "garbage collection"
+        do -- check that `output` does not allow gc of `input`
+            local input = source {}
 
-        set { "A", "C", "D" }
-
-        CHECK(find "A".Text == "1")
-        CHECK(not find "B")
-        CHECK(find "C".Text == "2")
-        CHECK(find "D".Text == "3")
-    end
-
-    do CASE "Use optional destructor"
-        local state, set = source { 1, 2, 3 }
-        local derived = map(state, function(i, v)
-            return { Value = v, Destroyed = false }
-        end, function(v)
-            v.Destroyed = true
-        end)
-
-        local first = derived()
-
-        CHECK(first[1].Destroyed == false)
-
-        set { 1, 2, 4 }
-
-        local _ = derived()
-
-        CHECK(first[1].Destroyed == false)
-        CHECK(first[2].Destroyed == false)
-        CHECK(first[3].Destroyed == true)
-    end
-
-    do CASE "Garbage collection"
-        do -- check that `derived` does not allow gc of `state`
-            local state = source {}
-
-            local derived = map(state, function(i, v)
+            local _derived = indexes(input, function(i, v)
                 return v
             end)
 
-            wref.state, state = state, nil :: any
-            wref.derived = derived
+            local wref = weak { input }
+
+            input = nil :: any
 
             gc()
-            CHECK(wref.state) 
+            CHECK(wref[1]) 
         end
 
-        do -- check that `state` allows gc of `derived`
-            local state = source {}
+        do -- check that `input` allows gc of `output`
+            local input = source {}
 
-            local derived = map(state, function(i, v)
+            local output = indexes(input, function(i, v)
                 return i, v
-            end) :: State?
+            end)
 
-            wref.state = state
-            wref.derived, derived = derived, nil
+            local wref = weak { output }
+
+            output = nil :: any
 
             gc()
-            CHECK(not wref.derived)
+            CHECK(not wref[1])
         end
-    end]]
+    end
 end)
 
 TEST("values()", function()
     local source = vide.source
     local values = vide.values
 
-    do CASE "Use state"
+    do CASE "use source"
         local input = source { 1, 2, 3 }
 
         local output = values(input, function(v, k)
@@ -1026,7 +928,7 @@ TEST("values()", function()
         CHECK("" .. input()[3] == output()[3])
     end
 
-    do CASE "Cache result"
+    do CASE "cache result"
         local input = source { 1, 2, 3 }
 
         local runcount = table.create(3, 0)
@@ -1047,7 +949,7 @@ TEST("values()", function()
         CHECK(runcount[3] == 1)
     end
 
-    do CASE "Removal reflected"
+    do CASE "removal reflected"
         local input = source { 1, 2, 3 }
 
         local output = values(input, function(v, i)
@@ -1063,7 +965,7 @@ TEST("values()", function()
         CHECK(t[3] == nil)
     end
 
-    do CASE "Removal reflected 2"
+    do CASE "removal reflected 2"
         local input = source { 1 }
 
         local output = values(input, function(v, i)
@@ -1088,7 +990,7 @@ TEST("spring()", function()
     local spring = vide.spring
     local watch = vide.watch
 
-    do CASE "Update state (on next hearbeat resumption cycle)"
+    do CASE "update source (on next step)"
         local value = source(10)
         local springed = spring(value, 1, 1)
 
@@ -1099,7 +1001,7 @@ TEST("spring()", function()
         CHECK(springed() > 10)
     end
 
-    do CASE "Garbage collection"
+    do CASE "garbage collection"
         do -- `output` should not allow gc of `input`
             local input = source(10)
             local _output = spring(input)
@@ -1124,7 +1026,7 @@ TEST("spring()", function()
     end
 
 
-    do CASE "Garbage collection (binded)"
+    do CASE "garbage collection (binded)"
         local input = source(10)
         local output = spring(input, 1, 1)
 
@@ -1139,7 +1041,7 @@ TEST("spring()", function()
         CHECK(wref[1]) -- `output` should not gc
     end
 
-    do CASE "Spring finished"
+    do CASE "spring finished"
         local input = source(0)
         local output = spring(input)
 
@@ -1166,11 +1068,11 @@ TEST("spring()", function()
     end
 end)
 
-TEST("Events", function()
+TEST("events", function()
     local create = vide.create
 
     local function Thing(props)
-        local instance = Instance.new("Thing") :: any
+        local instance = Instance.new("Thing")
         instance.Signal = Signal.new()
 
         local clone = create(instance)(props)
@@ -1178,7 +1080,7 @@ TEST("Events", function()
         return clone
     end
 
-    do CASE "Connect event"
+    do CASE "connect event"
         local connected = false
 
         local val = Thing {
@@ -1188,8 +1090,6 @@ TEST("Events", function()
             end
         }
 
-        -- testkit.print2(getmetatable(val))
-
         CHECK(not connected)
         val.Value = 1; Signal.fire(val.Signal, val.Value)
         CHECK(connected)
@@ -1200,7 +1100,7 @@ TEST("actions", function()
     local create = vide.create
     local action = vide.action
 
-    do CASE "Run action"
+    do CASE "run action"
         local ran = false
 
         create "Frame" {
@@ -1212,7 +1112,7 @@ TEST("actions", function()
         CHECK(ran)
     end
 
-    do CASE "Priorities"
+    do CASE "priorities"
         local queue = {}
 
         create "Frame" {
@@ -1235,8 +1135,9 @@ TEST("strict", function()
     local source = vide.source
     local derive = vide.derive
     local watch = vide.watch
+    local indexes, values = vide.indexes, vide.values
 
-    do CASE "Error on derived callback yield"
+    do CASE "error on derived callback yield"
         local state = source(1)
 
         local ok = pcall(function()
@@ -1249,7 +1150,7 @@ TEST("strict", function()
         CHECK(not ok)
     end
 
-    do CASE "Error on watcher callback yield"
+    do CASE "error on watcher callback yield"
         local state = source(1)
 
         local ok = pcall(function()
@@ -1262,7 +1163,7 @@ TEST("strict", function()
         CHECK(not ok)
     end
 
-    do CASE "Run derived callback twice"
+    do CASE "run derived callback twice"
         local state = source(1)
         local runcount = 0
 
@@ -1276,7 +1177,7 @@ TEST("strict", function()
         CHECK(runcount == 4)
     end
 
-    do CASE "Run watcher callback twice"
+    do CASE "run watcher callback twice"
         local state = source(1)
         local runcount = 0
 
@@ -1290,7 +1191,25 @@ TEST("strict", function()
         CHECK(runcount == 4)
     end
 
-    -- todo: add case for strict mode bindings
+    do CASE "indexes() error if primitive"
+        local state = source { 1 }
+
+        local ok = pcall(function()
+            indexes(state, function() return 1 end)
+        end)
+
+        CHECK(not ok)
+    end
+
+    do CASE "values() error if duplicate"
+        local state = source { 1, 2, 1 }
+
+        local ok = pcall(function()
+            values(state, function() return {} end)
+        end)
+
+        CHECK(not ok)
+    end
 end)
 
 local ok = FINISH()
diff --git a/todo.md b/todo.md
index 34a4b15..2cfdc63 100644
--- a/todo.md
+++ b/todo.md
@@ -3,9 +3,10 @@
 - cleanup codebase
 - setup site, improve docs
 - cleanup within `values()` and `indexes()`
+- behavior when a table source value is set to the same table
 - address behavior of binding property to multiples states
 - strict mode
-  - better error reporting
+  - better error reporting and stack traces
   - warn when `values()` returns primitive
   - warn when `values()` returns duplicate object
 - implement from solid