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diff --git a/src/astro_test.cc b/src/astro_test.cc
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+// Copyright 2022 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "src/astro.h"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <chrono>
+
+#include "third_party/date/include/date/tz.h"
+
+namespace glplanet {
+namespace {
+
+using ::testing::DoubleNear;
+using ::testing::Pair;
+
+TEST(SunEquatorialPositionTest, MeeusExercise25A) {
+  // October 13, 1992, at 00:00:00 TDT (T = -0.072'183'436)
+  constexpr auto t =
+      std::chrono::time_point<date::tai_clock, std::chrono::milliseconds>() +
+      std::chrono::days(34 * 365 + 8 /* leap days */) +
+      std::chrono::days(31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 11) +
+      std::chrono::hours(23) + std::chrono::minutes(59) +
+      std::chrono::milliseconds(27'816);
+  EXPECT_THAT(SunEquatorialPosition(t), Pair(DoubleNear(-2.82078673, 1e-8),
+                                             DoubleNear(-0.1358751, 1e-8)));
+}
+
+TEST(ApparentSiderealTimeAtGreenwichTest, MeeusExercise12A) {
+  // April 10, 1987, at 00:00:00 UT (T = -0.127'296'372'348)
+  constexpr auto t =
+      std::chrono::time_point<date::tai_clock, std::chrono::milliseconds>() +
+      std::chrono::days(29 * 365 + 7 /* leap days */) +
+      std::chrono::days(31 + 28 + 31 + 8) + std::chrono::hours(23) +
+      std::chrono::minutes(59) + std::chrono::milliseconds(27'816);
+  EXPECT_THAT(ApparentSiderealTimeAtGreenwich(t), DoubleNear(-2.832805, 1e-6));
+}
+
+TEST(HighNoonLocationTest, MarchEquinox) {
+  // March 20, 2022 15:29:52.331 UT
+  constexpr auto t =
+      std::chrono::time_point<date::tai_clock, std::chrono::milliseconds>() +
+      std::chrono::days(64 * 365 + 16 /* leap days */) +
+      std::chrono::days(31 + 28 + 19) + std::chrono::hours(15) +
+      std::chrono::minutes(29) + std::chrono::milliseconds(24'515);
+  EXPECT_THAT(HighNoonLocation(t),
+              Pair(DoubleNear(-0.883655431852, 1e-10), DoubleNear(0.0, 1e-10)));
+}
+
+}  // namespace
+}  // namespace glplanet