diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 60dad30..40efa24 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -21,7 +21,7 @@ Thank you for your interest in contributing to **PhDamage** - a floating combat
 ## Prerequisites
 
 - World of Warcraft client (Retail, TBC Anniversary, MoP Classic, Cata, or Classic)
-- [Lua 5.1](https://www.lua.org/) (for linting and testing)
+- [Lua 5.1](https://www.lua.org/) or [Lua 5.4](https://www.lua.org/) (for linting and testing)
 - [Luacheck](https://github.com/mpeterv/luacheck) (for static analysis)
 - [Busted](https://olivinelabs.com/busted/) (for unit tests)
 - [Git](https://git-scm.com/)
@@ -116,11 +116,18 @@ luacheck path/to/File.lua    # single file for fast feedback
 ### Automated Tests
 PhDamage uses [busted](https://olivinelabs.com/busted/) for unit testing. Tests live in the `tests/` directory.
 
+CI still runs tests with Lua 5.1. Local runs may use Lua 5.1 or Lua 5.4.
+
+Use the repo-local launcher instead of calling `busted` directly. Invoke it with whichever interpreter you want to verify, such as `lua`, `lua5.1`, or `lua5.4`. The launcher asks LuaRocks where `busted.runner` is installed and prepends that rock tree to `package.path` and `package.cpath` for the active interpreter.
+
 ```bash
-busted --verbose              # run all tests
-busted tests/some_spec.lua    # run a single test file
+lua tests/RunBusted.lua --verbose            # run all tests
+lua tests/RunBusted.lua tests/some_spec.lua  # run a single test file
+lua5.4 tests/RunBusted.lua --verbose         # explicitly test under Lua 5.4
 ```
 
+If `busted --verbose` fails with `module 'busted.runner' not found`, your `busted` wrapper and your active interpreter are using different module paths. The launcher above avoids that mismatch without hard-coded machine-specific paths.
+
 ### Manual Testing
 1. Load the addon in the target game version
 2. Attack a target dummy to verify floating combat text
diff --git a/Data/SpellData_Warlock.lua b/Data/SpellData_Warlock.lua
index 4717c40..2bf4653 100644
--- a/Data/SpellData_Warlock.lua
+++ b/Data/SpellData_Warlock.lua
@@ -450,7 +450,8 @@ SpellData[1949] = {
 -------------------------------------------------------------------------------
 
 -- Life Tap — instant, Shadow (converts health to mana)
--- Coefficient: ~0.8 (gains spell power scaling)
+-- Current addon model uses a 0.8 coefficient for the spell line, including Rank 6 at level 70.
+-- Revisit only if stronger in-game evidence shows this model is wrong.
 SpellData[1454] = {
     name = "Life Tap",
     school = SCHOOL_SHADOW,
diff --git a/tests/RunBusted.lua b/tests/RunBusted.lua
new file mode 100644
index 0000000..12d24c7
--- /dev/null
+++ b/tests/RunBusted.lua
@@ -0,0 +1,98 @@
+-------------------------------------------------------------------------------
+-- RunBusted.lua
+-- Repo-local Busted launcher that bootstraps LuaRocks paths for the active Lua
+--
+-- Supported versions: Retail, MoP Classic, TBC Anniversary, Cata, Classic
+-------------------------------------------------------------------------------
+
+local io = io
+local package = package
+local table = table
+
+local ACTIVE_LUA_VERSION = (_VERSION and _VERSION:match("(%d+%.%d+)"))
+    or error("Could not detect active Lua version", 0)
+
+local function Trim(value)
+    return (value:gsub("^%s+", ""):gsub("%s+$", ""))
+end
+
+local function ReadFirstLine(command)
+    local handle = io.popen(command)
+    if not handle then
+        return nil, "Failed to start command: " .. command
+    end
+
+    local output = handle:read("*a") or ""
+    local ok, _, code = handle:close()
+    local firstLine = Trim((output:match("([^\r\n]+)") or ""))
+
+    if firstLine == "" then
+        if ok or code == 0 then
+            return nil, "Command returned no output: " .. command
+        end
+
+        return nil, "Command failed: " .. command
+    end
+
+    return firstLine
+end
+
+local function PrependPath(currentValue, entries)
+    return table.concat(entries, ";") .. ";" .. currentValue
+end
+
+local function BootstrapLuaRocksPaths()
+    local runnerPath, runnerErr = ReadFirstLine(
+        "luarocks --lua-version " .. ACTIVE_LUA_VERSION .. " which busted.runner"
+    )
+    if not runnerPath then
+        return nil, runnerErr
+    end
+
+    runnerPath = runnerPath:gsub("\\", "/")
+
+    local rocksRoot, luaVersion = runnerPath:match("^(.*)/share/lua/(%d+%.%d+)/busted/runner%.lua$")
+    if not rocksRoot then
+        return nil, "Could not derive LuaRocks tree from: " .. runnerPath
+    end
+
+    if luaVersion ~= ACTIVE_LUA_VERSION then
+        return nil, "LuaRocks resolved busted for Lua " .. luaVersion
+            .. " but active lua is " .. ACTIVE_LUA_VERSION
+    end
+
+    package.path = PrependPath(package.path, {
+        rocksRoot .. "/share/lua/" .. luaVersion .. "/?.lua",
+        rocksRoot .. "/share/lua/" .. luaVersion .. "/?/init.lua",
+    })
+
+    package.cpath = PrependPath(package.cpath, {
+        rocksRoot .. "/lib/lua/" .. luaVersion .. "/?.dll",
+        rocksRoot .. "/lib/lua/" .. luaVersion .. "/?.so",
+    })
+
+    return true
+end
+
+local function RunBusted()
+    local ok, runner = pcall(require, "busted.runner")
+    if ok then
+        return runner({ standalone = false })
+    end
+
+    local originalError = runner
+    local _, bootstrapErr = BootstrapLuaRocksPaths()
+    if bootstrapErr then
+        error("Failed to load busted.runner. Original error: " .. tostring(originalError)
+            .. " | Bootstrap error: " .. tostring(bootstrapErr), 0)
+    end
+
+    ok, runner = pcall(require, "busted.runner")
+    if not ok then
+        error("Failed to load busted.runner after LuaRocks bootstrap: " .. tostring(runner), 0)
+    end
+
+    return runner({ standalone = false })
+end
+
+RunBusted()
diff --git a/tests/test_spellcalc.lua b/tests/test_spellcalc.lua
index 6b711a0..1837f16 100644
--- a/tests/test_spellcalc.lua
+++ b/tests/test_spellcalc.lua
@@ -293,6 +293,19 @@ describe("SpellCalc", function()
 
                 assert.is_near(0.8, result.coefficient, 0.0001)
             end)
+
+            it("should preserve the current modeled 0.8 scaling for Rank 6", function()
+                local spellData = ns.SpellData[1454]
+                local rankData = spellData.ranks[6]
+                local result = SpellCalc.ComputeBase(spellData, rankData, playerState)
+
+                local expectedSpBonus = 0.8 * 1000  -- 800
+                local expectedManaGain = 420 + expectedSpBonus  -- 1220
+
+                assert.is_near(expectedSpBonus, result.spellPowerBonus, 0.01)
+                assert.is_near(expectedManaGain, result.manaGain, 0.01)
+                assert.is_near(0.8, result.coefficient, 0.0001)
+            end)
         end)
 
         it("should return nil for an unknown spell type", function()