test: ztest: Add scalar power unit test converted from CMock

This patch converts 1 existing math advanced function unit test from
CMock/Unity to Zephyr's Ztest framework, maintaining the same test
coverage and functionality:

- test_math_arithmetic_power_fixed: Fixed-point scalar power function

Original test converted from
sof/test/cmocka/src/math/arithmetic/scalar_power.c authored by:
- Shriram Shastry <malladi.sastry@linux.intel.com>

The converted test validates the same power_int32() function from
src/math/power.c as the original CMock test, ensuring no regression in
test coverage during the migration to Ztest framework. Reference tables
and tolerance values are preserved to maintain identical test accuracy
and validation criteria.

Test validates 384 combinations (64 base values × 6 exponent values)
using MATLAB-generated reference data with fixed-point arithmetic:
- Base values: Q6.25 format (range -1.0 to 1.0)
- Exponent values: Q2.29 format
- Results: Q16.15 format
- Tolerance: max error 0.000034912111005, THD+N -96.457180359025074

This is part of the broader SOF unit test migration from CMock to Zephyr
Ztest framework, establishing the foundation for math/advanced/functions
tests in the new directory structure.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>

Author: tmleman

test/ztest/unit/math/advanced/functions/CMakeLists.txt

@@ -0,0 +1,35 @@
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(test_math_advanced_functions)
+
+set(SOF_ROOT "${PROJECT_SOURCE_DIR}/../../../../../..")
+
+# Include SOF CMake utilities for proper SOF source compilation
+include(${SOF_ROOT}/scripts/cmake/misc.cmake)
+
+target_include_directories(app PRIVATE
+	${SOF_ROOT}/zephyr/include
+	${SOF_ROOT}/src/include
+	${SOF_ROOT}/src/platform/library/include
+	${SOF_ROOT}/test/cmocka/include
+)
+
+# Define SOF-specific configurations for unit testing
+target_compile_definitions(app PRIVATE
+	-DCONFIG_SOF_LOG_LEVEL=CONFIG_LOG_DEFAULT_LEVEL
+	-DCONFIG_ZEPHYR_POSIX=1
+	-DCONFIG_LIBRARY=1
+	-DUNIT_TEST=1
+)
+
+target_sources(app PRIVATE
+	test_scalar_power_ztest.c
+	${SOF_ROOT}/src/math/power.c
+)
+
+# Apply SOF relative path definitions for proper compilation
+sof_append_relative_path_definitions(app)
+
+# Link math library for advanced math functions
+target_link_libraries(app PRIVATE m)

test/ztest/unit/math/advanced/functions/test_scalar_power_ztest.c

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// Copyright(c) 2025 Intel Corporation. All rights reserved.
+//
+// These contents may have been developed with support from one or more Intel-operated
+// generative artificial intelligence solutions.
+//
+// Converted from CMock to Ztest
+//
+// Original test from sof/test/cmocka/src/math/arithmetic/scalar_power.c:
+// Author: Shriram Shastry <malladi.sastry@linux.intel.com>
+
+#include <zephyr/ztest.h>
+#include <zephyr/logging/log.h>
+#include <sof/audio/format.h>
+#include <sof/math/power.h>
+#include <sof/common.h>
+#include <math.h>
+
+LOG_MODULE_REGISTER(test_scalar_power, LOG_LEVEL_INF);
+
+/* Test data tables from MATLAB-generated reference */
+#include "power_tables.h"
+
+/* Error tolerance: max error = 0.000034912111005, THD+N = -96.457180359025074 */
+#define CMP_TOLERANCE 0.0000150363575813f
+
+/**
+ * @brief Test scalar power function with fixed-point arithmetic
+ *
+ * This test validates the power_int32() function against MATLAB-generated
+ * reference values. It tests 64 base values against 6 exponent values,
+ * checking that the fixed-point power calculation stays within acceptable
+ * tolerance.
+ *
+ * Base values: Fixed-point Q6.25 format (range -1.0 to 1.0)
+ * Exponent values: Fixed-point Q2.29 format
+ * Result: Fixed-point Q16.15 format
+ */
+ZTEST(math_advanced_functions_suite, test_math_arithmetic_power_fixed)
+{
+	double p;
+	int i;
+	int j;
+
+	for (i = 0; i < ARRAY_SIZE(b); i++) {
+		for (j = 0; j < ARRAY_SIZE(e); j++) {
+			p = power_int32(b[i], e[j]);
+			float delta = fabsf((float)(power_table[i][j] - (double)p / (1 << 15)));
+
+			zassert_true(delta <= CMP_TOLERANCE);
+		}
+	}
+}
+
+ZTEST_SUITE(math_advanced_functions_suite, NULL, NULL, NULL, NULL, NULL);