Refine observation assertion messages for keys (#4768)

Closes gh-4046

Author: izeye

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/ObservationContextAssert.java

@@ -229,6 +229,11 @@ private List<String> highCardinalityKeys() {
     public SELF hasLowCardinalityKeyValueWithKey(String key) {
         isNotNull();
         if (this.actual.getLowCardinalityKeyValues().stream().noneMatch(tag -> tag.getKey().equals(key))) {
+            if (this.actual.getHighCardinalityKeyValue(key) != null) {
+                failWithMessage(
+                        "Observation should have a low cardinality tag with key <%s> but it was in the wrong (high) cardinality keys. List of all low cardinality keys <%s>",
+                        key, lowCardinalityKeys());
+            }
             failWithMessage(
                     "Observation should have a low cardinality tag with key <%s> but it's not there. List of all keys <%s>",
                     key, lowCardinalityKeys());
@@ -301,6 +306,11 @@ public SELF doesNotHaveLowCardinalityKeyValue(KeyValue keyValue) {
     public SELF hasHighCardinalityKeyValueWithKey(String key) {
         isNotNull();
         if (this.actual.getHighCardinalityKeyValues().stream().noneMatch(tag -> tag.getKey().equals(key))) {
+            if (this.actual.getLowCardinalityKeyValue(key) != null) {
+                failWithMessage(
+                        "Observation should have a high cardinality tag with key <%s> but it was in the wrong (low) cardinality keys. List of all high cardinality keys <%s>",
+                        key, highCardinalityKeys());
+            }
             failWithMessage(
                     "Observation should have a high cardinality tag with key <%s> but it's not there. List of all keys <%s>",
                     key, highCardinalityKeys());

micrometer-observation-test/src/test/java/io/micrometer/observation/tck/ObservationContextAssertTests.java

@@ -253,6 +253,22 @@ void should_throw_exception_when_low_cardinality_key_value_missing() {
             .isInstanceOf(AssertionError.class);
     }
 
+    @Test
+    void should_throw_exception_when_low_cardinality_key_value_missing_but_in_high_cardinality_keys() {
+        Observation observation = Observation.start("foo", context, registry);
+        observation.lowCardinalityKeyValue("low", "l");
+        observation.highCardinalityKeyValue("high", "h");
+
+        thenThrownBy(() -> assertThat(context).hasLowCardinalityKeyValue("high", "h"))
+            .isInstanceOf(AssertionError.class)
+            .hasMessage(
+                    "Observation should have a low cardinality tag with key <high> but it was in the wrong (high) cardinality keys. List of all low cardinality keys <[low]>");
+        thenThrownBy(() -> assertThat(context).hasLowCardinalityKeyValueWithKey("high"))
+            .isInstanceOf(AssertionError.class)
+            .hasMessage(
+                    "Observation should have a low cardinality tag with key <high> but it was in the wrong (high) cardinality keys. List of all low cardinality keys <[low]>");
+    }
+
     @Test
     void should_not_throw_exception_when_high_cardinality_key_value_exists() {
         Observation observation = Observation.start("foo", context, registry);
@@ -273,6 +289,22 @@ void should_throw_exception_when_high_cardinality_key_value_missing() {
             .isInstanceOf(AssertionError.class);
     }
 
+    @Test
+    void should_throw_exception_when_high_cardinality_key_value_missing_but_in_low_cardinality_keys() {
+        Observation observation = Observation.start("foo", context, registry);
+        observation.lowCardinalityKeyValue("low", "l");
+        observation.highCardinalityKeyValue("high", "h");
+
+        thenThrownBy(() -> assertThat(context).hasHighCardinalityKeyValue("low", "l"))
+            .isInstanceOf(AssertionError.class)
+            .hasMessage(
+                    "Observation should have a high cardinality tag with key <low> but it was in the wrong (low) cardinality keys. List of all high cardinality keys <[high]>");
+        thenThrownBy(() -> assertThat(context).hasHighCardinalityKeyValueWithKey("low"))
+            .isInstanceOf(AssertionError.class)
+            .hasMessage(
+                    "Observation should have a high cardinality tag with key <low> but it was in the wrong (low) cardinality keys. List of all high cardinality keys <[high]>");
+    }
+
     @Test
     void should_not_throw_exception_when_high_cardinality_key_value_present() {
         thenNoException().isThrownBy(() -> assertThat(context).doesNotHaveHighCardinalityKeyValue("foo", "bar")