test: created assertions module and use it for positions discoverer

Author: rcasia

tests/assertions.lua

@@ -0,0 +1,74 @@
+local M = {}
+
+--- Recursively convert a table to a formatted string with indentation.
+---@param value any
+---@param indent? integer
+---@return string
+local function pretty(value, indent)
+	indent = indent or 0
+	local t = type(value)
+
+	if t == "table" then
+		local pad = string.rep("  ", indent)
+		local buf = { "{" }
+		for k, v in pairs(value) do
+			local key_str = tostring(k)
+			local val_str = pretty(v, indent + 1)
+			table.insert(buf, string.format("\n%s  [%s] = %s", pad, key_str, val_str))
+		end
+		table.insert(buf, "\n" .. pad .. "}")
+		return table.concat(buf, "")
+	elseif t == "string" then
+		return string.format("%q", value)
+	else
+		return tostring(value)
+	end
+end
+
+--- Deep equality comparison
+---@param a any
+---@param b any
+---@return boolean
+local function deep_equal(a, b)
+	if a == b then
+		return true
+	end
+	if type(a) ~= type(b) then
+		return false
+	end
+	if type(a) ~= "table" then
+		return false
+	end
+
+	local seen = {}
+	for k in pairs(a) do
+		seen[k] = true
+		if not deep_equal(a[k], b[k]) then
+			return false
+		end
+	end
+	for k in pairs(b) do
+		if not seen[k] then
+			return false
+		end
+	end
+	return true
+end
+
+--- Assert that two values are deeply equal, printing full diff if not.
+---@param expected any
+---@param actual any
+---@param msg? string
+function M.eq(expected, actual, msg)
+	if not deep_equal(expected, actual) then
+		local err = string.format(
+			"%s\nExpected:\n%s\n\nGot:\n%s",
+			msg or "Assertion failed (tables not equal):",
+			pretty(expected),
+			pretty(actual)
+		)
+		error(err, 2)
+	end
+end
+
+return M

tests/core/positions_discoverer_spec.lua

@@ -3,7 +3,9 @@ local _ = require("vim.treesitter") -- NOTE: needed for loading treesitter upfro
 local async = require("nio").tests
 local plugin = require("neotest-java")
 
-local eq = assert.are.same
+local assertions = require("tests.assertions")
+
+local eq = assertions.eq
 
 describe("PositionsDiscoverer", function()
 	local tmp_files