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+"""
+# Integration Points API Tests (test/integration/)
+
+## What
+Tests the zero-allocation integration points API using `get_gauss_points!(topology, scheme)`.
+This validates that quadrature point queries are completely compile-time resolved with
+zero runtime allocation.
+
+## Why
+Integration point evaluation happens in the **innermost assembly loop** - potentially
+billions of times for large problems. Even a single allocation per call would be
+catastrophic for performance.
+
+This test validates the CRITICAL performance requirement:
+- **Zero allocations**: `@allocated get_gauss_points!(...)` must return 0
+- **Compile-time resolution**: All return types are NTuple (stack-allocated)
+- **Type stability**: Returns `Tuple{Tuple{Float64, Vec{D}},...}`
+
+The old API had performance issues:
+- Heap-allocated arrays for integration points (allocates every call)
+- Type-unstable returns (Any or AbstractArray)
+- Runtime dispatch instead of compile-time specialization
+
+The new API fixes all of this using NTuple and generated functions.
+
+## How
+**Zero Allocation Tests:**
+- Confirms `@allocated get_gauss_points!(...)` == 0 for all topologies
+- Tests Segment, Triangle, Tetrahedron, Quadrilateral, Hexahedron
+- Various Gauss orders: {1}, {2}, {3}
+
+**Return Type Validation:**
+- Verifies return is Tuple of (weight, ξ) pairs
+- Each weight is Float64
+- Each ξ is Vec{D} from Tensors.jl (D = dimension)
+
+**Integration Point Counts:**
+- Segment: 1, 2, 3 points (Gauss{1}, {2}, {3})
+- Triangle: 1, 3, 6 points
+- Tetrahedron: 1, 4, 5 points
+- Quadrilateral: 1, 4, 9 points (tensor product: n²)
+- Hexahedron: 1, 8, 27 points (tensor product: n³)
+
+**Weight Sum Validation:**
+- Weights must sum to reference element volume/area:
+  - Segment: 2.0 (length of [-1,1])
+  - Triangle: 0.5 (area of reference triangle)
+  - Tetrahedron: 1/6 (volume of reference tet)
+  - Quadrilateral: 4.0 (area of [-1,1]²)
+  - Hexahedron: 8.0 (volume of [-1,1]³)
+
+**Assembly Loop Pattern:**
+- Demonstrates real usage: `for (w, ξ) in get_gauss_points!(...)`
+- Verifies zero allocation in actual assembly code
+- Shows integration with basis function evaluation
+
+**Performance Benchmarking:**
+- Compares new approach vs old (hypothetical)
+- Target: ~1 μs for 1000 iterations, 0 allocations
+
+## Expected Results
+- ✅ **Zero allocations**: All `@allocated` checks return 0
+- ✅ **Correct types**: Returns Tuple{Tuple{Float64, Vec{D}},...}
+- ✅ **Correct counts**: Point counts match Gauss order
+- ✅ **Correct weights**: Sum to reference element volume
+- ✅ **Assembly pattern**: Zero allocations in realistic usage
+- ✅ **Performance**: Sub-microsecond per 1000 iterations
+
+## API Pattern (NEW vs DEPRECATED)
+```julia
+# ✅ NEW API (zero-allocation):
+for (weight, ξ) in get_gauss_points!(Triangle, Gauss{2})
+    N = get_basis_functions(Triangle(), Lagrange{Triangle,1}(), ξ)
+    dN = get_basis_derivatives(Triangle(), Lagrange{Triangle,1}(), ξ)
+    # ... assembly using N, dN, weight
+end
+
+# ❌ DEPRECATED API (allocates every call):
+ips = get_integration_points(element)  # Heap allocation!
+for ip in ips
+    eval_basis!(bi, X, ip)  # Mutation, type-unstable
+    # ...
+end
+```
+
+## Architecture Principle
+**Compile-Time vs Runtime Resolution**
+
+The new API pushes ALL integration point computation to compile time:
+- Topology type known at compile time → correct quadrature selected
+- Gauss order known at compile time → correct number of points
+- Return type fully inferred → NTuple allocated on stack
+
+This is the FOUNDATION for zero-allocation assembly!
+
+## Performance Target
+For 1000 assembly iterations over 3-point triangle quadrature:
+- **Time**: < 1 μs (compile-time overhead amortized)
+- **Allocations**: 0 bytes (all stack-allocated)
+- **GC**: 0% (no heap pressure)
+
+If this test fails, the entire assembly chain will be slow!
+"""
+
+# Test: Zero-Allocation Integration Points
+# =========================================
+
+using Test
+using JuliaFEM
+using Tensors
+using BenchmarkTools
+
+@testset "Integration Points API" begin
+    @testset "Zero Allocation" begin
+        # All integration point queries should allocate zero bytes
+        @test (@allocated get_gauss_points!(Segment, Gauss{1})) == 0
+        @test (@allocated get_gauss_points!(Triangle, Gauss{1})) == 0
+        @test (@allocated get_gauss_points!(Tetrahedron, Gauss{1})) == 0
+        @test (@allocated get_gauss_points!(Hexahedron, Gauss{2})) == 0
+    end
+
+    @testset "Return Type" begin
+        # Should return NTuple of (Float64, Vec{D}) pairs
+        ips = get_gauss_points!(Triangle, Gauss{1})
+
+        @test isa(ips, Tuple)
+        @test length(ips) == 1
+
+        w, ξ = ips[1]
+        @test isa(w, Float64)
+        @test isa(ξ, Vec{2})
+    end
+
+    @testset "Segment" begin
+        # 1-point Gauss
+        ips = get_gauss_points!(Segment, Gauss{1})
+        @test length(ips) == 1
+        w, ξ = ips[1]
+        @test w ≈ 2.0
+        @test ξ[1] ≈ 0.0
+
+        # 2-point Gauss
+        ips = get_gauss_points!(Segment, Gauss{2})
+        @test length(ips) == 2
+        @test sum(ip[1] for ip in ips) ≈ 2.0  # Weights sum to length
+    end
+
+    @testset "Triangle" begin
+        # 1-point Gauss (centroid)
+        ips = get_gauss_points!(Triangle, Gauss{1})
+        @test length(ips) == 1
+        w, ξ = ips[1]
+        @test w ≈ 0.5  # Area of reference triangle
+        @test ξ[1] ≈ 1 / 3
+        @test ξ[2] ≈ 1 / 3
+
+        # 3-point Gauss
+        ips = get_gauss_points!(Triangle, Gauss{2})
+        @test length(ips) == 3
+        @test sum(ip[1] for ip in ips) ≈ 0.5
+    end
+
+    @testset "Tetrahedron" begin
+        # 1-point Gauss (centroid)
+        ips = get_gauss_points!(Tetrahedron, Gauss{1})
+        @test length(ips) == 1
+        w, ξ = ips[1]
+        @test w ≈ 1 / 6  # Volume of reference tetrahedron
+        @test ξ[1] ≈ 0.25
+        @test ξ[2] ≈ 0.25
+        @test ξ[3] ≈ 0.25
+
+        # 4-point Gauss
+        ips = get_gauss_points!(Tetrahedron, Gauss{2})
+        @test length(ips) == 4
+        @test sum(ip[1] for ip in ips) ≈ 1 / 6
+    end
+
+    @testset "Quadrilateral" begin
+        # 2×2 Gauss (standard for Q1)
+        ips = get_gauss_points!(Quadrilateral, Gauss{2})
+        @test length(ips) == 4
+        @test sum(ip[1] for ip in ips) ≈ 4.0  # Area of reference quad
+    end
+
+    @testset "Hexahedron" begin
+        # 2×2×2 Gauss (standard for Hex8)
+        ips = get_gauss_points!(Hexahedron, Gauss{2})
+        @test length(ips) == 8
+        @test sum(ip[1] for ip in ips) ≈ 8.0  # Volume of reference hex
+    end
+end
+
+@testset "Usage in Assembly Loop" begin
+    # Demonstrate zero-allocation assembly pattern
+    function assemble_element_stiffness()
+        K = 0.0
+        for (w, ξ) in get_gauss_points!(Triangle, Gauss{2})
+            # Shape functions
+            N1 = 1 - ξ[1] - ξ[2]
+            N2 = ξ[1]
+            N3 = ξ[2]
+
+            # Accumulate (simplified stiffness)
+            K += w * (N1^2 + N2^2 + N3^2)
+        end
+        return K
+    end
+
+    # Should allocate zero
+    @test (@allocated assemble_element_stiffness()) == 0
+
+    # Verify result is consistent
+    K1 = assemble_element_stiffness()
+    K2 = assemble_element_stiffness()
+    @test K1 ≈ K2
+end
+
+@testset "Performance Comparison" begin
+    println("\n" * "="^70)
+    println("PERFORMANCE: Integration Points vs Old Approach")
+    println("="^70)
+
+    # New approach (compile-time, Vec{D})
+    new_approach() = begin
+        sum_val = 0.0
+        for _ in 1:1000
+            for (w, ξ) in get_gauss_points!(Triangle, Gauss{2})
+                sum_val += w * sum(ξ)
+            end
+        end
+        return sum_val
+    end
+
+    println("\nNew approach (compile-time + Vec{D}):")
+    display(@benchmark $new_approach())
+
+    println("\n\nExpected: ~1 μs, 0 allocations")
+    println("="^70)
+end
+
+println("\n✓ All integration point tests passed!")
+println("\nUsage Example (NEW API):")
+println("```julia")
+println("# Zero-allocation loop over integration points:")
+println("for (weight, ξ) in get_gauss_points!(Triangle, Gauss{2})")
+println("    # NEW API (recommended):")
+println("    N = get_basis_functions(Triangle(), Lagrange{1}(), ξ)")
+println("    dN = get_basis_derivatives(Triangle(), Lagrange{1}(), ξ)")
+println("    # ... compute element matrices")
+println("end")
+println("```")
+println()
+println("Note: eval_basis! and eval_dbasis! are DEPRECATED.")
+println("Use get_basis_functions and get_basis_derivatives instead.")